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

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

Change-Id: I6d3b4ea454c5cdc21eb681ede76387f46b9fdb43