Test: Fix flaky PhonePolicyTest and ActiveDeviceManagerTest

* PhonePolicyTest needs to stub A2dpService.connect() and
  HeadsetService.connect() methods for it to pass stably
* Fixed a miscounted frequency for HeadsetService.setPriority()
  in PhonePolicyTes.testDisconnectNoAutoConnect().
* Fixed a race condition in ActiveDeviceManagerTest where dependency
  calls such as HearingAidService.setActiveDevice() happens before
  internal state such as mHearingAidActiveDevice is set. The fix
  requires ActiveDeviceManagerTest to wait for ActiveDeviceManager's
  handler looper to finish executing scheduled tasks before checking any
  internal states

Bug: 80437170
Test: run PhonePolicyTest, ActiveDeviceManagerTest 100 times
Change-Id: Iece11914c4c7f7c54abcbf78caa7ddd2ba1d740f