setup qtaguid group ownership of ctrl and stat files

This will help get rid of android_aid.h in the kernel.
The group of the proc entries will be used in place of the default
values picked up by the xt_qtaguid netfilter module
(AID_NET_BW_STATS, AID_NET_BW_ACCT).
This change has no effect until the matching kernel changes are
submitted.

Change-Id: I3c177e7b5caf9c59300eba6bd4a976634b333674