Wait for nova-compute to claim to be up

Even with wait conditions, it is hard to judge from inside the
nova-compute host that nova-compute has decided it is "up".

We can poll nova service-list to know that for sure however.

Change-Id: Ibad0faa24e7d551ef5e78a2e9c1bb8f7d31fa9d1
Closes-Bug: #1260543
Merge "Wait for nova-compute to claim to be up"