Whitelist new CHANGE_OVERLAY_PACKAGES permission

The Shell application needs access to change which overlays are
enabled in OverlayManagerService.

Test: Manual: invoke adb exec-out cmd overlay enable some.package.name
when shell is not root (adb unroot on eng builds).
Change-Id: I1849f68e244cfc9b1e13eb0e673dde7be03cba6d