servicemanager: Mark vndservicemanager as shutdown critical

vndservicemanager needs to be alive during shutdown to allow vndk
components which may run during shutdown to communicate. The system
ndk servicemanager keeps running throughout shutdown, so this brings
the vndservicemanager on par with that behavior.

Bug: 62951929, 63514363, 62845700
Test: Build
Change-Id: Iba154820ef69c6491a5cb05747b6b905763a825d
diff --git a/cmds/servicemanager/vndservicemanager.rc b/cmds/servicemanager/vndservicemanager.rc
index d5ddaaf..3fa4d7d 100644
--- a/cmds/servicemanager/vndservicemanager.rc
+++ b/cmds/servicemanager/vndservicemanager.rc
@@ -3,4 +3,4 @@
     user system
     group system readproc
     writepid /dev/cpuset/system-background/tasks
-
+    shutdown critical