Provide a way to clean up testing database

We will need to clean up stacks(hard delete) sometimes in the tests.
Resoure, ResourceData, and Event need to be cleaned up as well because
of the integrity constraints.

blueprint event-persistence

Change-Id: I355f7a9909eb3ad3febca62fdb57ecbaab73f2ce
Merge "Provide a way to clean up testing database"