[DO NOT MERGE] Reset mTrackingReportedValues in endSample()

Otherwise, when next SamplingTimer.update() is called, it will take
zero as start time.

Bug: 142466892
Test: NA.

Change-Id: I04625fadd8fd8bab3ba83b8e7cd10737ad34e60b
(cherry picked from commit c7d49e01)