Revert "BUG/MINOR: server: Remove FQDN requirement for using init-addr and state file"

This reverts commit 19e8aa58f7c42e602a95b4ceb4b254c424aed11c.

It causes some trouble reported by Manu :
   listen tls
     [...]
     server bla 127.0.0.1:8080

   [ALERT] 248/130258 (21960) : parsing [/etc/haproxy/test.cfg:53] : 'server bla' : no method found to resolve address '(null)'
   [ALERT] 248/130258 (21960) : Failed to initialize server(s) addr.

According to Nenad :
  "It's not a good way to fix the issue we were experiencing
   before. It will need a bigger rewrite, because the logic in
   srv_iterate_initaddr needs to be changed."
diff --git a/src/server.c b/src/server.c
index 67870b8..c80c987 100644
--- a/src/server.c
+++ b/src/server.c
@@ -4276,7 +4276,8 @@
 			goto srv_init_addr_next;
 
 		for (srv = curproxy->srv; srv; srv = srv->next)
-			return_code |= srv_iterate_initaddr(srv);
+			if (srv->hostname)
+				return_code |= srv_iterate_initaddr(srv);
 
  srv_init_addr_next:
 		curproxy = curproxy->next;