Previously, if we attempted to georeplicate storage from the existing location and, somehow, that existing location did not exist, we'd still mark the new location as invalid. This is a major problem for storage engines that are not consistent. Now, we first try a back off strategy to find the image in the existing storage and, as well, if the replication fails in any way, we log it.
- Switches database schema creation to alembic, which solves the MySQL issue (and makes sure we test migrations as well)
- Adds a few time.sleep(1) to work around MySQL's second-precision issue when adding items to queues and then immediately retrieving them
- Disables the storage proxy tests when running against non-SQLite databases, as it causes failures with the multiple process and multiple transactions
- Changes initdb to support only populating the database, as well as fixing a few small items around the test data when working with non-SQLite data
