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

test/test_storageproxy.py

@@ -47,6 +47,7 @@ class TestStorageProxy(LiveServerTestCase):
     self.test_app.config['DISTRIBUTED_STORAGE_PREFERENCE'] = ['test']
     return self.test_app
 
+  @unittest.skipIf(os.environ.get('TEST_DATABASE_URI'), "not supported for non SQLite testing")
   def test_storage_proxy_auth_notinstalled(self):
     # Active direct download on the fake storage.
     self.storage.put_content(['test'], 'supports_direct_download', 'true')
@@ -65,6 +66,7 @@ class TestStorageProxy(LiveServerTestCase):
     self.assertEquals(404, resp.status_code)
 
 
+  @unittest.skipIf(os.environ.get('TEST_DATABASE_URI'), "not supported for non SQLite testing")
   def test_storage_proxy_auth(self):
     # Active direct download on the fake storage.
     self.storage.put_content(['test'], 'supports_direct_download', 'true')