Use FLAG_IMMUTABLE for ServiceStateTracker

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: If127b73c975b5b3f004500de7f9baa6a7bc00ce4
Merged-In: If127b73c975b5b3f004500de7f9baa6a7bc00ce4
1 file changed