Use FLAG_IMMUTABLE for CarrierServiceStateTracker

Require that the PendingIntent be immutable so that a malicious app is
 not able to hijack and mutate any of the details.

Test: Android builds
Bug: 155094269
Change-Id: Iea9ec6451170e592dc72c035d6eec7b80150ddd4
Merged-In: Iea9ec6451170e592dc72c035d6eec7b80150ddd4
1 file changed