Allow blocking calls to ActivityController

ActivityControllers are used in tests (e.g. monkeys), therefore
we are not concerned about misbehaving activity controllers on
production devices.

Fixes: 147705653
Test: run a monkey to ensure that activities can still start and
  there are no ONEWAY_FLAG warnings from BinderProxy

Change-Id: If14c17e821106e27b562e2ddf76edfd3bdcdd80a