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.
```
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