MINOR: server: Make 'default-server' support 'tcp-ut' keyword.

This patch makes 'default-server' directive support 'tcp-ut' keyword.
diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index 4741651..b664831 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -1833,7 +1833,7 @@
 
 static struct srv_kw_list srv_kws = { "TCP", { }, {
 #ifdef TCP_USER_TIMEOUT
-	{ "tcp-ut",        srv_parse_tcp_ut,        1,  0 }, /* set TCP user timeout on server */
+	{ "tcp-ut",        srv_parse_tcp_ut,        1,  1 }, /* set TCP user timeout on server */
 #endif
 	{ NULL, NULL, 0 },
 }};