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

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

Change-Id: I6749ecdc5cc0d355d27385326f81749d2ebfbac4