VMware: pass vm_ref to _get_and_set_vnc_config

In the spawn refactor we get the vm_ref when the instance is created.
Passing it to the method _get_and_set_vnc_config saves a function
call. We are able to do this as we already have the vm_ref for the
instance in question.

Change-Id: I7b8d056af7f49ebd31beff2876edb9e6115d0a2c
Merge "VMware: pass vm_ref to _get_and_set_vnc_config"