Android N IOT Preview 2 (NIG40)
dhcp client: create class SocketUtil to simplify class DHCPV4

This takes part of the code for socket handling out of class
DHCPV4.
The new class SocketUtil is a helper class for creating
sockets and sending packet through socket.
while there, this also fixes a typo for broadcast address.

Bug: 25642025
TEST=compile, and test using python scripts

Change-Id: I5ae3018498bfbfa23f6e50c72c4845be808ba5c4
6 files changed