Fix use of stale instance data in compute manager

There's a number of cases of using stale instance data in the compute
manager.  Ie, there are a lot of calls to self._instance_update() that
ignore the response and use a stale copy of data from that point
forward.

Related to bug 1098727

That bug id is for 'reboot_instance' only, so there's a separate patch
to fix that method.

Change-Id: Ifec6bf23831b51c8679528428ee475c906c1f536
Merge "Fix use of stale instance data in compute manager"