Add ActivityThreadClientTest to presubmit

Add tests to presubmit and mark as flaky. We will remove
the flaky annotation if stable.

Bug: 143153552
Test: atest FrameworksMockingCoreTests:android.app.activity.
      ActivityThreadClientTest
Change-Id: Ife07cfc8891184dcb6cf2b8444cd36fbfad7fdc9