Automatic merge from submit-queue

Specify subnetid and routetableid via cloud provider config

**What this PR does / why we need it**:
This is a fix for https://github.com/kubernetes/kubernetes/pull/39996 which is needed since 1.6

Changes introduced from 1.6 broke partially(LoadBalancer) the support for running the master components in a different environment (different aws account/on premise). This PR will add support for specifying the Subnet & RouteTable to use via the cloud provider config.

**Release note**:

```release-note
AWS cloud provider: fix support running the master with a different AWS account or even on a different cloud provider than the nodes.
```