Ensure that all tasks for a test finish before starting next test.

This would avoid tasks getting executed after mocks have been cleared,
and reduce the chances of cross test interactin.

Adding it to one test to begin with to ensure this is WAI.

Bug: 288343906
Test: atest HealthFitnessUnitTests
Change-Id: Ib623259ba2e21b8faa3238da22d5d0a855552f08
4 files changed