Handle service creation race by service workers

This handle a race where a sibling has already created the service
record in the database.  This fix is similar to that of commit
f6c341b4.

Change-Id: I7975fc632eee34390c5d7dc275b52363ad45475e
Closes-bug: 1326901
(cherry picked from commit 37247aba813fbc408901a2f1b1ad88e2acb796a1)
Turn periodic tasks off in all unit tests

We shouldn't rely on periodic tasks to randomly run in unit tests,
instead if we need them to run we should explicitly call them out.

Change-Id: I35850c47288e50d3146771dc7a9a54d62e36c3cf
Related-Bug: 1311778
(cherry picked from commit f3f07f4401ff8be25598493c088e4e100b387fe4)
Prevent clean-up of migrating instances on compute init

During compute manager startup init_host is called. One
of the functions this carries out is to delete instance
data that doesn't belong to this host this function only
checks if the local instance belongs to the host or not.
It doesn't check the task_state. This could result in the
loss of all instance data if it occured at the wrong
point during live migration.

This change checks if the task_state of the instance to
be deleted is MIGRATING and if so it does not delete the
instance. Similarily for the task state RESIZE_MIGRATING.

This change adjust little about the unit test according to
actual code path in icehouse.
Conflicts:
	nova/tests/compute/test_compute_mgr.py

Change-Id: Ia8c67acf93d71af868907f0711dcc1dfe103560c
Closes-Bug: 1319797
(cherry picked from commit 340cae5466eaf5568c4f0eecb2a2fa7cdbcc0ba4)
Merge "Prevent clean-up of migrating instances on compute init" into stable/icehouse
Merge "Turn periodic tasks off in all unit tests" into stable/icehouse
Merge "Handle service creation race by service workers" into stable/icehouse