Add SET_WALLPAPER permission to SystemUI

If an exception is thrown in updateWallpaperLocked, a call to
WallpaperManager.clear() is made.  This requires the SET_WALLPAPER
permission and will throw a SecurityException if that permission
is not granted to SystemUI.

Change-Id: I61811b65dcfe8b15f0e9030f7aa6d1dc09cea351
ChooseTypeAndAccountActivity: Fix the Null pointer Exception of monkey test

ChooseTypeAndAccountActivity crashed during monkey test, due to Null
pointer exception occurred.

To fix this issue, Add Null pointer check before we use it.

CRs-Fixed: 478250

Change-Id: Iae3e331edfda238ecb0c6d5d32b15329b1dfee0b