Since Glance doesn't yet have rolling upgrades, nor is the tooling
idempotent, we avoid running the database operations during minor
upgrades to maintain uptime.
Major upgrades will still run the sync operations, and the database will
be synced if there is no existing database regardless of the type of
upgrade.
Change-Id: I4a4d8f23f05a16d25878340ede019be7ccdb7196