RDMA/nes: Change state to closing after FIN

When the driver receives an AE for FIN received, it closes the
connection without changing the state of the connection in the
hardware to closing.  By changing the state to closing, hardware will
do a normal close sequence.

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