compositor-drm: Disable planes when zoomed or capturing

When the entire output is transformed or we're capturing the output
for screenshot or video, disable all output specific overlays
(drm planes, hw cursors etc) and move all surfaces into the primary
plane.
diff --git a/src/compositor.c b/src/compositor.c
index fe595e6..5be5789 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -1148,14 +1148,12 @@
 		}
 	}
 
-	if (output->assign_planes)
-		/*
-		 * This will queue flips for the fbs and sprites where
-		 * applicable and clear the damage for those surfaces.
-		 * The repaint loop below will repaint everything
-		 * else.
-		 */
+	if (output->assign_planes && !output->disable_planes)
 		output->assign_planes(output);
+	else
+		wl_list_for_each(es, &ec->surface_list, link)
+			weston_surface_move_to_plane(es, &ec->primary_plane);
+
 
 	pixman_region32_init(&opaque);