Do not emit the broken mode twice if exec is called

Add more tests

test/helper.js

@@ -145,5 +145,15 @@ module.exports = {
                 func();
             }
         };
+    },
+    killConnection: function (client) {
+        // Change the connection option to a non existing one and destroy the stream
+        client.connectionOption = {
+            port: 6370,
+            host: '127.0.0.2',
+            family: 4
+        };
+        client.address = '127.0.0.2:6370';
+        client.stream.destroy();
     }
 };