Sync network_info if instance not found before _build_resources yield

If instance is deleted before _build_resources yield, there won't
waiting for network_info sync finish.

So there is race case, when the exception catching for
'InstanceNotFound' in do_build_and_run_instance invoke
'_cleanup_allocated_networks', the '_allocate_network_async' didn't
create port yet. After '_cleanup_allocated_networks' finished,
'_allocate_network_async' create new port for the instance, but there
isn't any cleanup for the new port anymore.

Change-Id: I5027a1aaeb9a2106f7982fd0422f88c4caa20ffb
Related-Bug: #1357055
Merge "Sync network_info if instance not found before _build_resources yield"