Prevent loop in PermissionPolicyService

The AppOpsModeChangeWatchers call back even if the mode was set to
already set mode. PermissionPolicyService listens to the same app-ops it
changes. I.e. it used to change the mode to default, which then causes a
call-back which made set it to default again, etc...

This exhausts a thread until the app-op is finally set to non-default.
The fix is to prevent the loop by checking if the app-op is already the
correct mode before setting it.

Fixes: 135674928
Test: atest IncidentReportListenerTest CollectorHostsideLibTest on
          cuttlefish and crosshatch
Change-Id: Ic65945e814957ac59495b3da221fabb0f3d42b66