This is a required patch.

Kilo introduced a nova-api database but didn't use it. [1]
Mitaka now uses it and has broken booting instances. [2]

[1] https://wiki.openstack.org/wiki/ReleaseNotes/Kilo#OpenStack_Compute_.28Nova.29
[2] https://github.com/openstack/nova/blob/df0fca62cf5324f5b6eae0fed1f88c6c9ed61c71/releasenotes/notes/request-spec-api-db-b9cc6e0624d563c5.yaml

Change-Id: If0a7f4ba4937fab8d60f5236ca00db06faa768c7
Closes-Bug: #1540579