Add the FLAG_IMMUTABLE flag for creating a PendingIntent

- Android S+ to specify explicitly either FLAG_MUTABLE or FLAG_IMMUTABLE
  when creating a PendingIntent.

Fixes: 170162598
Fixes: 170162878
Fixes: 170163592
Fixes: 170164316
Fixes: 170164458
Fixes: 170164327
Fixes: 169794524
Fixes: 170165106
Test: build pass and manual test add an account
Change-Id: I0f7b117273647dbe9e146033b8995c8c6f147576