credstore: update credstore.rc to use correct class, user, and group.

Bug: 111446262
Test: Manually inspected
Change-Id: If99f55fcd6034e059d8d7100a94ec59fb6c66a72
diff --git a/identity/credstore.rc b/identity/credstore.rc
index 12c1e72..d9e989a 100644
--- a/identity/credstore.rc
+++ b/identity/credstore.rc
@@ -1,5 +1,4 @@
 service credstore /system/bin/credstore /data/misc/credstore
-    class main
-    user keystore
-    group keystore drmrpc readproc log
-    writepid /dev/cpuset/foreground/tasks
\ No newline at end of file
+    class core
+    user credstore
+    group credstore