raw ip: fix race of two connect(2)

The historical design of sockets is that on a re-connect the disconnect is
performed at the socket layer in soconnectat().  Since SMP times this is
known to be racy and the function has appopriate comment.  I missed that
in the recent change.  The pr_connect method should normally expect the
socket to be already disconnected, however should be able to handle a race
where socket is actually connected.  Convert the check that incorrectly
tried to handle normal path of re-connect into check that handles the
race.

Reported by:	markj
Fixes:	ece716c5d3

sys/netinet/raw_ip.c

@@ -904,8 +904,7 @@ rip_connect(struct socket *so, struct sockaddr *nam, struct thread *td)
 	KASSERT(inp != NULL, ("rip_connect: inp == NULL"));
 
 	INP_WLOCK(inp);
-	if (inp->inp_faddr.s_addr != INADDR_ANY &&
-	    addr->sin_addr.s_addr == INADDR_ANY)
+	if (__predict_false(inp->inp_faddr.s_addr != INADDR_ANY))
 		rip_dodisconnect(inp, false);
 	if (addr->sin_addr.s_addr != INADDR_ANY) {
 		inp->inp_faddr = addr->sin_addr;