Add support to clear DB
Add support to clear DB

Fixes bug 1171740

The method cleanup() can be called when a test is complete,
for example in the tearDown method.

Change-Id: Id30bcb0d7ef167f6cb3b1bdea06f6421e1234a86

malor/oslo.db,openstack/oslo.db,vikt0rs/oslo.db,JioCloud/oslo.db,openstack/oslo.db,akash1808/oslo.db,varunarya10/oslo.db,magic0704/oslo.db