All the compute and cloud tests work.

Scheduler tests still need to be updated.

I also added support for making a single request with the old syntax
work (i.e.: instance_uuids not set). I think it might be too
much to support the old num_instances request. since we know that
a num_instances request > 1 will always be a call from the compute
host, if we happen to have an old request, perhaps we could raise
a reasonable exception?

i.e.
legacy_num_instances = request_spec.get('num_instances', 1)
if legacy_num_instances != 1:
    raise Invalid("Not supported")

The alternative is to leave all the db create code in the schedulers
and allow them to support both versions.

Change-Id: Ibef8a40bc037102d67841ebc2751f00284c50353