af_iucv: Test additional sk states in iucv_sock_shutdown

Add few more sk states in iucv_sock_shutdown().
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/iucv/af_iucv.c

@@ -937,6 +937,9 @@ static int iucv_sock_shutdown(struct socket *sock, int how)
 
 	lock_sock(sk);
 	switch (sk->sk_state) {
+	case IUCV_DISCONN:
+	case IUCV_CLOSING:
+	case IUCV_SEVERED:
 	case IUCV_CLOSED:
 		err = -ENOTCONN;
 		goto fail;