Don't give drmserver read permission to local storage

o related-to-bug: 6426185

Change-Id: Ibacd9210d10f95e3b5586dfa671c0b32d24f47de
diff --git a/rootdir/init.rc b/rootdir/init.rc
index c7063b5..984c8f7 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -428,7 +428,7 @@
 service drm /system/bin/drmserver
     class main
     user drm
-    group drm system inet drmrpc sdcard_r
+    group drm system inet drmrpc
 
 service media /system/bin/mediaserver
     class main