don't clear the database dicts in the tearDown method
don't clear the database dicts in the tearDown method

This is superfluous as the two dicts (self.engines and
self.test_databases) are re-initialised during setUp anyway and aren't
used in between

Change-Id: Icafa9bdf3b0193f31752e6104ecac0e49476c812

n0ano/gantt,n0ano/gantt