Don't panic in TCP_linger() if the other end closed on us.

Fixes #547



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@4384 d4fa192b-c00b-0410-8231-f00ffab90ce4

lib/libvarnish/tcp.c

@@ -240,8 +240,10 @@ void
 TCP_linger(int sock, int linger)
 {
 	struct linger lin;
+	int i;
 
 	memset(&lin, 0, sizeof lin);
 	lin.l_onoff = linger;
-	AZ(setsockopt(sock, SOL_SOCKET, SO_LINGER, &lin, sizeof lin));
+	i = setsockopt(sock, SOL_SOCKET, SO_LINGER, &lin, sizeof lin);
+	assert(i == 0 || errno == EBADF);
 }