Prevent non-system overlays from showing over CDM UI

Since CDM grants privileges, it should have the same overlay
policy as permission UI

Test: use an app wit ha visible overlay to ensure
the overlay disappears when CDM is shown
Fixes: 171221090
Change-Id: I004843edf5a156dc07fb961edf80272f5cb50163
(cherry picked from commit ea4ce4d48eb22e05f03b36e281149f1e944674fa)
(cherry picked from commit 3c2fece4a52512c7dc7a0101bc6b435c44490450)
1 file changed