clear recovery framebuffers on allocation; display icon right after ui_init

Make ui_init() clear the framebuffer memory it maps in so the user
isn't treated to a visible flash of random bits on recovery startup.
Call ui_set_background() (to show the installing icon) right after
ui_init() to display something while device_recovery_start() is
working (which can take a second or two on some devices).

Bug: 3145331
Change-Id: I11e7859fab5847370ea4f4932c3fb1558af26c5d
diff --git a/recovery.c b/recovery.c
index 452794a..9ad075d 100644
--- a/recovery.c
+++ b/recovery.c
@@ -701,6 +701,7 @@
     printf("Starting recovery on %s", ctime(&start));
 
     ui_init();
+    ui_set_background(BACKGROUND_ICON_INSTALLING);
     load_volume_table();
     get_args(&argc, &argv);