RDMA/nes: Fix terminate connection

Fixes a crash that occurs during close when error async event is received.
Terminate message is not sent to the remote node if already processing close.

Signed-off-by: Tatyana Nikolova <Tatyana.E.Nikolova@intel.com>
Signed-off-by: Faisal Latif <Faisal.Latif@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>