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

This patch makes 'default-server' directive support 'tcp-ut' keyword.
diff --git a/src/server.c b/src/server.c
index 2bba49f..42a45c6 100644
--- a/src/server.c
+++ b/src/server.c
@@ -13,6 +13,7 @@
 
 #include <ctype.h>
 #include <errno.h>
+#include <netinet/tcp.h>
 
 #include <import/xxhash.h>
 
@@ -1435,6 +1436,10 @@
 				newsrv->ssl_ctx.ciphers = strdup(curproxy->defsrv.ssl_ctx.ciphers);
 #endif
 
+#ifdef TCP_USER_TIMEOUT
+			newsrv->tcp_ut = curproxy->defsrv.tcp_ut;
+#endif
+
 			cur_arg = 3;
 		} else {
 			newsrv = &curproxy->defsrv;