dhcp client: support unicast for renewing and release
RFC 2131 requires the DHCP client to send unicast packet
to DHCP server upon renewing and release.
This create a new udp socket for sending unicast packet.
In this way kernel can fill the destination mac address
for us.
This also renames the old socket name to raw_socket.
This also fix the condition for sending dhcp release and
clearing sockets.
Bug: 25642025
TEST=compile, and test using python scripts
Change-Id: I2a984ebe8f4e3870426deaa149fe4c8abe79c9e7
2 files changed
