Fix full database test script to not fail randomly

- 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

workers/storagereplication.py

@@ -5,7 +5,6 @@ import time
 from app import app, storage, image_replication_queue
 from data.database import CloseForLongOperation
 from data import model
-from storage.basestorage import StoragePaths
 from workers.queueworker import QueueWorker, WorkerUnhealthyException
 
 logger = logging.getLogger(__name__)