Fix listener search functions

The functions that searched for listeners compared both sockets and
addresses in the same function. This made its use error prone and caused
false positives in some cases.

server/core/config_runtime.cc

@@ -1172,7 +1172,7 @@ bool runtime_create_listener(Service* service,
     {
         config_runtime_error("Listener '%s' already exists", name);
     }
-    else if (SListener l = listener_find_by_config("", addr, u_port))
+    else if (SListener l = listener_find_by_address(addr, u_port))
     {
         config_runtime_error("Listener '%s' already listens on [%s]:%u", l->name(), addr, u_port);
     }