Remove get_vif_by_mac_address from network rpcapi

This method is no longer used.  It was added to network.api and runs on
the API side now instead.  We can remove it from the rpc client code.
We can later remove it from the manager side when we do a major version
bump of this rpc API.

Change-Id: I8933bcc022558a9befed7478047422959fa47f1c
Merge "Remove get_vif_by_mac_address from network rpcapi"