Fix OS-123, support for gc-install-agent on instances with multiple IPs.

Tested on a dual network instance:
f626b14c-fc81-4e94-a1cb-c9bda643e8ef | first test | ACTIVE | 10.0.19.3, 64.x.y.z

The 10.* address is unreachable from us, the 64.* address is a floating IP.

Change-Id: I3eac69858f2111d467faa6b3deb126d5c82d7bb5
Added launch_index to instance_ref in _copy_instance

This fixes an issue where cloud-init wouldn't run in
launched instances because there was no ami-launch-index
meta-data.

Change-Id: I690297eb4fe1cf57bae509019505448ceb16105c