init.rc: launch update_verifier with exec_start

This allows update_verifier to raise it's priority and ioprio.

Bug: 36511808
Bug: 36102163
Test: Boot bullhead
Test: Verify boottime decrease on sailfish
Change-Id: I5710c6a98dc7acee9063d1fa1d1c80668f0f1528
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 7091ab9..d48b892 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -598,7 +598,7 @@
 
 on nonencrypted
     # A/B update verifier that marks a successful boot.
-    exec - root cache -- /system/bin/update_verifier nonencrypted
+    exec_start update_verifier_nonencrypted
     class_start main
     class_start late_start
 
@@ -621,12 +621,12 @@
 
 on property:vold.decrypt=trigger_restart_min_framework
     # A/B update verifier that marks a successful boot.
-    exec - root cache -- /system/bin/update_verifier trigger_restart_min_framework
+    exec_start update_verifier
     class_start main
 
 on property:vold.decrypt=trigger_restart_framework
     # A/B update verifier that marks a successful boot.
-    exec - root cache -- /system/bin/update_verifier trigger_restart_framework
+    exec_start update_verifier
     class_start main
     class_start late_start