RDMA/nes: Fix stale ARP issue

When the remote node's ethernet address changes, the connection keeps
trying to connect using the old address.  The connection wil continue
failing until the driver is unloaded and loaded again (eiter reboot or
rmmod).  Fix this by checking that the NIC has the correct address
before starting a connection.

Signed-off-by: Faisal Latif <faisal.latif@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>