BUG: Do not throw exception in Probes with mis-matched Stop

With the model of a stop watch as the expected behavior, hitting the
stop button multiple times has not effect.

Change-Id: Id1ade7e5e8a70ed9c9a08b5af48a7730399f7ab0
Merge topic 'FixTimeProbeStopException'

b5deb6d7 BUG: Do not throw exception in Probes with mis-matched Stop