Revert "Revert "storaged: assign to system-background cpuset""

This reverts commit b7ef979639d4d5a590d4a4615bd39e987f900c13.

Change-Id: Ib9478701c67dbddf2f76480ae6ca6e0a9145a778
diff --git a/storaged/storaged.rc b/storaged/storaged.rc
index 5fdbb8a..a8fa5a7 100644
--- a/storaged/storaged.rc
+++ b/storaged/storaged.rc
@@ -2,3 +2,4 @@
     class main
     file /d/mmc0/mmc0:0001/ext_csd r
     group root readproc
+    writepid /dev/cpuset/system-background/tasks