Always destroy RegionSamplingHelper on same thread

stopAndDestroy() was being called from the main thread, while
registration was happening on the background. This would lead to
concurrency bugs because this class is not thread safe.

Test: atest RegionSamplingHelperTest
Fixes: 201962411
Change-Id: I01290f5931972ad3eb322e7dddc44e002324e405
2 files changed