nvmet-tcp: fix unhandled tcp states in nvmet_tcp_state_change()

TCP_FIN_WAIT2 and TCP_LAST_ACK were not handled, the connection is closing
so we can ignore them and avoid printing the "unhandled state"
warning message.

[ 1298.852386] nvmet_tcp: queue 2 unhandled state 5
[ 1298.879112] nvmet_tcp: queue 7 unhandled state 5
[ 1298.884253] nvmet_tcp: queue 8 unhandled state 5
[ 1298.889475] nvmet_tcp: queue 9 unhandled state 5

v2: Do not call nvmet_tcp_schedule_release_queue(), just ignore
the fin_wait2 and last_ack states.

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>