net/smc: improve close of terminated socket

Make sure a terminated SMC socket reaches the CLOSED state.
Even if sending of close flags fails, change the socket state to
the intended state to avoid dangling sockets not reaching the
CLOSED state.

Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>