LockscreenWallpaper was set to null on NotificationMediaManager because
StatusBar#mWallpaperSupported was not initialized yet.
Fixes: 146252300
Test: manual
Change-Id: I4c5151ad6b40d0f0996fdbb825745729cc003425
Merged-In: I4c5151ad6b40d0f0996fdbb825745729cc003425