Clean unrelated error of two tests
Clean unrelated error of two tests

When running test test_check_alarm_query_constraints and
test_start_singleton, a NoneType error will be raised, that is because the
tests invoked the real aodh.storage.get_connection_from_config method.

Change-Id: I00932eda921d15bb9e59f1f82631e5ad7bb4f93d

openstack/aodh,openstack/aodh