Fix the mStopTimeNs not be reset in Stopwatch#Restart

Bug: 151796056
Test: atest NetworkStackIntegrationTests NetworkStackTests
Test: atest FrameworksNetTests
Test: Manual test with statsd_testdrive
Original-Change: https://android-review.googlesource.com/1343438
Merged-In: Ib83ceb70af3491dacbb4a45f65ef38661ae75e32
Change-Id: Ib83ceb70af3491dacbb4a45f65ef38661ae75e32
3 files changed