libsysutils: fix null pointer and memory leak issue

In SocketClient::quoteArg function
1. Fix potential null pointer accessing issue
2. Fix potential memory leak introduced by realloc fail

Change-Id: I1ca0f9089290d43452e9a71428244545f4ed866b
Signed-off-by: Hong-Mei Li <a21834@motorola.com>
init.rc: 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
fix bad return value in dhcp_do_request_*

1. bad return status make it return uninitialized prefixLength with a magic
number in android_net_utils_runDhcpCommon()
2. it will make DhcpInfoInternal.makeLinkAddress() to throw
IllegalArgumentException when try to connect a Wifi AP
3. the exception will make system reboot, of cource it random.

Change-Id: Iabc0cd5b69c1316f4eeae0aa1b8a91444dca4562
Signed-off-by: Michael Wu <michaelstay@gmail.com>