Mitigate the app visibility gap

The API #packageHasActiveAdmins leaves the possibility that malicious
code could do a side channel attack. Apply the app visibility check
to mitigate this.

Bug: 204786752
Test: atest CtsAdminTestCases
Test: atest FrameworksServicesTests:DevicePolicyManagerTest
Test: manually using the PoC in the buganizer to ensure the symptom
      no longer exists.
Change-Id: Icb7134706f8b1a1fc6d0145a2023ca779c76eb7b