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>
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>
Merge branch 'jb-mr1' of https://github.com/AOKP/system_core into linaro