IMMS: Make IMMS PendingIntents immutable Fixes: 154913391 Test: n/a Change-Id: I34a95732ef3e7c20d6549b57230c11f0c3db04d6 Merged-In: I34a95732ef3e7c20d6549b57230c11f0c3db04d6 (cherry picked from commit d4b625994f7664666ac7b53bf6a7d79a6459b3f1) (cherry picked from commit 6842f03c9d2f128785df5ce2bd02c61f35226554)