Fix tests on postgresql (#3740)

.travis.yml

changelog.d/3740.misc

tests/handlers/test_device.py

tests/replication/slave/storage/_base.py

tests/replication/slave/storage/test_account_data.py

tests/replication/slave/storage/test_events.py

tests/replication/slave/storage/test_receipts.py

tests/server.py

tests/storage/test_appservice.py

tests/storage/test_directory.py

tests/storage/test_event_federation.py

tests/storage/test_monthly_active_users.py

tests/storage/test_presence.py

tests/storage/test_profile.py

tests/storage/test_user_directory.py

tests/test_visibility.py

tests/unittest.py

tests/utils.py