Fix crash of test after finishing RecentsAnimationTest

The scheduleIdleLocked may be called when updating visibility
of activity. That will cause a mocked record to be used in
unexpected invocations.

Also block until the test thread has completed the pending
messages to prevent the execution from overlapping with the
next test.

Fix: 134891465
Test: atest RecentsAnimationTest
Change-Id: I339505ee75ba6e67aa8668dd4e40aef0f74df2aa