Add CTS test for useTargetActivityForQuickAccess() method in QAWService.

The test covers 3 cases:
* Metadata doesn't exist
* Metadata exists and is true
* Metadata exists and is false

In each case, we set the appropriate service as default, bind to it,
then call the method and assert the value.

This involves a bit of a change to TestQuickAccessWalletService:
* Added an override in onBind to count down when the device is bound.
  I think we probably meant to have this from the start, but we never
  did. We have the same thing for unbind, so I genuinely think this was
  a bug.

* Update the reference to the service in onBind instead of onCreate.
  This makes more sense semantically since we want the reference to be
  to the currently bound service, instead of the most recently created
  one.

Bug: 218860062
Test: atest QuickAccessWalletServiceTest
Test: atest
Change-Id: Ia779f382b0c2059e1c1ae47f0760ab944a9ab153
5 files changed