Use FLAG_IMMUTABLE for InstallCarrierAppUtils

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: I8ac155bf53e33474e1fcdb2466743a1e05b92399
Merged-In: I8ac155bf53e33474e1fcdb2466743a1e05b92399
1 file changed