When aborting tcp_attach() due to a problem allocating or attaching the

tcpcb, lock the inpcb before calling in_pcbdetach() or in6_pcbdetach(),
as they expect the inpcb to be passed locked.

MFC after:	7 days

sys/netinet/tcp_usrreq.c

@@ -1211,6 +1211,8 @@ tcp_attach(so)
 		int nofd = so->so_state & SS_NOFDREF;	/* XXX */
 
 		so->so_state &= ~SS_NOFDREF;	/* don't free the socket yet */
+
+		INP_LOCK(inp);
 #ifdef INET6
 		if (isipv6)
 			in6_pcbdetach(inp);