Make WallpaperMS bind wallpaper component PendingIntent immutable. am: 178da54fc9 am: 6ea3559233 am: 5b295c7726 am: b3fd083cb1 am: 254924da94

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

Change-Id: I3dde790cb91c34073396ff7c16e19ee55a59b74c