Automatic merge from submit-queue

apiserver latency reductions

Combined effect of these two commits on the latency observed by the 1000-node kubemark benchmark:

```
name                               old ms/op  new ms/op   delta
LIST_nodes_p50                      127 ±16%    121 ± 9%   -4.58%  (p=0.000 n=29+27)
LIST_nodes_p90                      326 ±12%    266 ±12%  -18.48%  (p=0.000 n=29+27)
LIST_nodes_p99                      453 ±11%    400 ±14%  -11.79%  (p=0.000 n=29+28)
LIST_replicationcontrollers_p50    29.4 ±49%   26.2 ±54%     ~     (p=0.085 n=30+29)
LIST_replicationcontrollers_p90    83.0 ±78%   68.6 ±59%  -17.33%  (p=0.013 n=30+28)
LIST_replicationcontrollers_p99     216 ±43%    177 ±49%  -17.68%  (p=0.000 n=29+29)
DELETE_pods_p50                    24.5 ±14%   24.3 ±13%     ~     (p=0.562 n=30+29)
DELETE_pods_p90                    30.7 ± 1%   30.7 ± 1%   -0.30%  (p=0.011 n=29+29)
DELETE_pods_p99                    77.2 ±34%   54.2 ±23%  -29.76%  (p=0.000 n=30+27)
PUT_replicationcontrollers_p50     5.86 ±26%   5.94 ±32%     ~     (p=0.734 n=29+29)
PUT_replicationcontrollers_p90     15.8 ± 7%   15.5 ± 6%   -2.06%  (p=0.010 n=29+29)
PUT_replicationcontrollers_p99     57.8 ±35%   39.5 ±55%  -31.60%  (p=0.000 n=29+29)
PUT_nodes_p50                      14.9 ± 2%   14.8 ± 2%   -0.68%  (p=0.012 n=30+27)
PUT_nodes_p90                      16.5 ± 1%   16.3 ± 2%   -0.90%  (p=0.000 n=27+28)
PUT_nodes_p99                      57.9 ±47%   41.3 ±35%  -28.61%  (p=0.000 n=30+28)
POST_replicationcontrollers_p50    6.35 ±29%   6.34 ±20%     ~     (p=0.944 n=30+28)
POST_replicationcontrollers_p90    15.4 ± 5%   15.0 ± 5%   -2.18%  (p=0.001 n=29+29)
POST_replicationcontrollers_p99    52.2 ±71%   32.9 ±46%  -36.99%  (p=0.000 n=29+27)
POST_pods_p50                      8.99 ±13%   8.95 ±16%     ~     (p=0.903 n=30+29)
POST_pods_p90                      16.2 ± 4%   16.1 ± 4%     ~     (p=0.287 n=29+29)
POST_pods_p99                      30.9 ±21%   26.4 ±12%  -14.73%  (p=0.000 n=28+28)
POST_bindings_p50                  9.34 ±12%   8.92 ±15%   -4.54%  (p=0.013 n=30+28)
POST_bindings_p90                  16.6 ± 1%   16.5 ± 3%   -0.73%  (p=0.017 n=28+29)
POST_bindings_p99                  23.5 ± 9%   21.1 ± 4%  -10.09%  (p=0.000 n=27+28)
PUT_pods_p50                       10.8 ±11%   10.2 ± 5%   -5.47%  (p=0.000 n=30+27)
PUT_pods_p90                       16.1 ± 1%   16.0 ± 1%   -0.64%  (p=0.000 n=29+28)
PUT_pods_p99                       23.4 ± 9%   20.9 ± 9%  -10.93%  (p=0.000 n=28+27)
DELETE_replicationcontrollers_p50  2.42 ±16%   2.50 ±13%     ~     (p=0.054 n=29+28)
DELETE_replicationcontrollers_p90  11.5 ±12%   11.8 ±13%     ~     (p=0.141 n=30+28)
DELETE_replicationcontrollers_p99  19.5 ±21%   19.1 ±21%     ~     (p=0.397 n=29+29)
GET_nodes_p50                      0.77 ±10%   0.76 ±10%     ~     (p=0.317 n=28+28)
GET_nodes_p90                      1.20 ±16%   1.14 ±24%   -4.66%  (p=0.036 n=28+29)
GET_nodes_p99                      11.4 ±48%    7.5 ±46%  -34.28%  (p=0.000 n=28+29)
GET_replicationcontrollers_p50     0.74 ±17%   0.73 ±17%     ~     (p=0.222 n=30+28)
GET_replicationcontrollers_p90     1.04 ±25%   1.01 ±27%     ~     (p=0.231 n=30+29)
GET_replicationcontrollers_p99     12.1 ±81%  10.0 ±145%     ~     (p=0.063 n=28+29)
GET_pods_p50                       0.78 ±12%   0.77 ±10%     ~     (p=0.178 n=30+28)
GET_pods_p90                       1.06 ±19%   1.02 ±19%     ~     (p=0.120 n=29+28)
GET_pods_p99                       3.92 ±43%   2.45 ±38%  -37.55%  (p=0.000 n=27+25)
LIST_services_p50                  0.20 ±13%   0.20 ±16%     ~     (p=0.854 n=28+29)
LIST_services_p90                  0.28 ±15%   0.27 ±14%     ~     (p=0.219 n=29+28)
LIST_services_p99                  0.49 ±20%   0.47 ±24%     ~     (p=0.140 n=29+29)
LIST_endpoints_p50                 0.19 ±14%   0.19 ±15%     ~     (p=0.709 n=29+29)
LIST_endpoints_p90                 0.26 ±16%   0.26 ±13%     ~     (p=0.274 n=29+28)
LIST_endpoints_p99                 0.46 ±24%   0.44 ±21%     ~     (p=0.111 n=29+29)
LIST_horizontalpodautoscalers_p50  0.16 ±15%   0.15 ±13%     ~     (p=0.253 n=30+27)
LIST_horizontalpodautoscalers_p90  0.22 ±24%   0.21 ±16%     ~     (p=0.152 n=30+28)
LIST_horizontalpodautoscalers_p99  0.31 ±33%   0.31 ±38%     ~     (p=0.817 n=28+29)
LIST_daemonsets_p50                0.16 ±20%   0.15 ±11%     ~     (p=0.135 n=30+27)
LIST_daemonsets_p90                0.22 ±18%   0.21 ±25%     ~     (p=0.135 n=29+28)
LIST_daemonsets_p99                0.29 ±28%   0.29 ±32%     ~     (p=0.606 n=28+28)
LIST_jobs_p50                      0.16 ±16%   0.15 ±12%     ~     (p=0.375 n=29+28)
LIST_jobs_p90                      0.22 ±18%   0.21 ±16%     ~     (p=0.090 n=29+26)
LIST_jobs_p99                      0.31 ±28%   0.28 ±35%  -10.29%  (p=0.005 n=29+27)
LIST_deployments_p50               0.15 ±16%   0.15 ±13%     ~     (p=0.565 n=29+28)
LIST_deployments_p90               0.22 ±22%   0.21 ±19%     ~     (p=0.107 n=30+28)
LIST_deployments_p99               0.31 ±27%   0.29 ±34%     ~     (p=0.068 n=29+28)
LIST_namespaces_p50                0.21 ±25%   0.21 ±26%     ~     (p=0.768 n=29+27)
LIST_namespaces_p90                0.28 ±29%   0.26 ±25%     ~     (p=0.101 n=30+28)
LIST_namespaces_p99                0.30 ±48%   0.29 ±42%     ~     (p=0.339 n=30+29)
LIST_replicasets_p50               0.15 ±18%   0.15 ±16%     ~     (p=0.612 n=30+28)
LIST_replicasets_p90               0.22 ±19%   0.21 ±18%   -5.13%  (p=0.011 n=28+27)
LIST_replicasets_p99               0.31 ±39%   0.28 ±29%     ~     (p=0.066 n=29+28)
LIST_persistentvolumes_p50         0.16 ±23%   0.15 ±21%     ~     (p=0.124 n=30+29)
LIST_persistentvolumes_p90         0.21 ±23%   0.20 ±23%     ~     (p=0.092 n=30+25)
LIST_persistentvolumes_p99         0.21 ±24%   0.20 ±23%     ~     (p=0.053 n=30+25)
LIST_resourcequotas_p50            0.16 ±12%   0.16 ±13%     ~     (p=0.175 n=27+28)
LIST_resourcequotas_p90            0.20 ±22%   0.20 ±24%     ~     (p=0.388 n=30+28)
LIST_resourcequotas_p99            0.22 ±24%   0.22 ±23%     ~     (p=0.575 n=30+28)
LIST_persistentvolumeclaims_p50    0.15 ±21%   0.15 ±29%     ~     (p=0.079 n=30+28)
LIST_persistentvolumeclaims_p90    0.19 ±26%   0.18 ±34%     ~     (p=0.446 n=29+29)
LIST_persistentvolumeclaims_p99    0.19 ±26%   0.18 ±34%     ~     (p=0.446 n=29+29)
LIST_pods_p50                      68.0 ±16%   56.3 ± 9%  -17.19%  (p=0.000 n=29+28)
LIST_pods_p90                       119 ±19%     93 ± 8%  -21.88%  (p=0.000 n=28+28)
LIST_pods_p99                       230 ±18%    202 ±14%  -12.13%  (p=0.000 n=27+28)
```