Replace Thread.sleep() with TestLooper.moveTimeForward()

TestLooper.moveTimeForward() changes the target delivery time of the messages
in the queue to simulate elapsed time. This allows tests to run faster in a
more deterministic way without incurring the indeterminism caused by Thread.sleep()
which is usually a source of flakiness and should be avoided when possible.

Bug: 140208026
Test: atest PackageWatchdogTest
Change-Id: I3365093838ec9fa2de5742359f6947379add7703