Mock out action event calls in build instance test

action_event_start() and action_event_finish() get called during the
build instance tests and if we time out call()s in the fake RPC driver
when there are no consumers for a topic, then these tests will fail.

blueprint: oslo-messaging
Change-Id: Ib109fa9552dc6032b390c300723bb6cb72d62062
Merge "Mock out action event calls in build instance test"