Pan: Prevent native call from within the test

There is no check / no pre-requisite about the native state while
running a service test for instrumentations. Mocking the interface and
preventing the calls to be made should prevent the test to fail.

Note that there are still 2 calls to native being done: init and cleanup

Bug: 295103561
Bug: 294642435
Test: atest PanServiceTest | This was already passing when run alone
Test: atest BluetoothInstrumentationTests | Previous test were making it
      fail
Change-Id: I6aaeb9fd340cd9afd0616b1b478877efded00162