Automatic merge from submit-queue

Trusty: Add debug supports for docker and kubelet

This PR adds debug support in two aspects: (1) For a test cluster, docker command will have "--debug" flag. Recently we noticed that this is very helpful in debug e2e test failures; (2) The kubelet command line will be put in /etc/default/kubelet. If a developer wants to test kubelet flags without recreating a cluster, she/he only needs to revise this file and then run "initctl restart kubelet". In addition, this PR fixes a couple of small things like comments and alignment.

Test result:
(1) Manually verified changing /etc/default/kubelet and run "initctl restart kubelet";
(2) Verified docker command line flag "--debug";
(3) e2e on pure trusty cluster and hybrid cluster all passed.

@roberthbailey @dchen1107 @zmerlynn please review it.

cc/ @yujuhong @fabioy @wonderfly FYI.