A race condition is caused when nova-compute is started for the
first time because it takes a period of time for nova-compute
to spin up, register itself with nova API, and become available for
cell enrollment.
Prior to this there was no wait condition when nova-compute
restarts occurred, so the first time nova-compute started, often
the compute service was not registered in the database and available
for cell enrollment when the enrollment tasks ran.
Change-Id: I510f0a957f53d15affa1fc23f809abff52208438
b9b8e08ac0