rfclient: Include missing headers

Signed-off-by: Joe Stringer <joestringernz@gmail.com>
FlowTable: Don't block when sending ARP requests

We currently resolve gateway MAC addresses by attempting to initiate a
TCP connection with the gateway. This causes the OS to perform ARP for
the gateway IP. However, the connection generally does not establish,
which makes RTPoller block waiting for the TCP connection to timeout.
This patch makes the socket non-blocking, which should speed up gateway
resolution.

Signed-off-by: Joe Stringer <joestringernz@gmail.com>