Properly destroy the dns_handler socket when first start fails

To correctly exit the process

src/main.cpp

@@ -196,8 +196,13 @@ int main(int ac, char** av)
             }
         }
       else
+        {
+#ifdef UDNS_FOUND
+          dns_handler.destroy();
+#endif
           identd.shutdown();
         }
+    }
     // If the only existing connection is the one to the XMPP component:
     // close the XMPP stream.
     if (exiting && xmpp_component->is_connecting())