vmwareapi: Add supported_instances to host state

The VMWareVCDriver uses the VCState class to report host state,
but VCState.update_status() does not include supported_instances.
Add supported_instances to the data returned by update_status(),
similar to HostState.update_status().

Change-Id: I15c0f930dd9e540f6fdb0d7246661a0c98e35ed4
Merge "vmwareapi: Add supported_instances to host state"