livedisplay: Fix racy init

* It turns out moving this to class main doesn't work as well
  as some had thought it would, so restore the previous logic
  to use class hal, and restart if the backend isn't up yet

Change-Id: Ib8b417d89108dcf80d0d159e8d84e5327944b2a1

hidl/livedisplay/vendor.lineage.livedisplay@2.1-service.oplus.rc

@@ -1,4 +1,4 @@
 service vendor.livedisplay-hal-2-1 /vendor/bin/hw/vendor.lineage.livedisplay@2.1-service.oplus
-    class hal
+    class late_start
     user system
     group system