Fix "Not all flavors have been migrated to the API database"

Fix "Not all flavors have been migrated to the API database"

After a successful upgrade to Newton, I ran the tripleo.sh
--overcloud-pingtest and it failed with the following:

resources.test_flavor: Not all flavors have been migrated to the API database (HTTP 409)

The issue is the fact that some tables have migrated to the
nova_api db and we need to migrate the data as well.

Currently we do:
    nova-manage db sync
    nova-manage api_db sync

We want to add:
    nova-manage db online_data_migrations

After launching this command the overcloud-pingtest works correctly:
tripleo.sh -- Overcloud pingtest SUCCEEDED

Change-Id: Id2d5b28b5d4ade7dff6c5e760be0f509b4fe5096
Closes-Bug: #1628450