This update clears up an additional path that was mentioned in the
Advanced Configuration documentation, but not actually picked up in the
playbooks.

This specifically affects Service Configuration overrides. The docs have
been cleaned up to reflect the way the playbooks pick up the override
files.

Change-Id: Id15fe139af6462217c2ac26d7d21c5eac5368e12
Closes-Bug: 1873782
Signed-off-by: Raimund Hook <openstack@sting-ray.za.net>