Make WallpaperMS bind wallpaper component PendingIntent immutable. am: 178da54fc9 am: 6ea3559233 am: 5b295c7726 am: b3fd083cb1

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/12718925

Change-Id: I5cae667d955f7cf02180d1a30ee8cbff976f5bfb