This has come up a few times via support questions from operators
that have a nova cell database out of sync with the placement
database resulting in a mismatch in compute nodes to provider
uuids and they just want to wipe the placement database and rebuild
it from the current data in nova. This provides a document with the
high level steps to do that.
Change-Id: Ie4fed22615f60e132a887fe541771c447fae1082
1a17fe8aab