Add close() method in MasterSlaveConnection.php

lib/Doctrine/DBAL/Connections/MasterSlaveConnection.php

@@ -280,6 +280,17 @@ class MasterSlaveConnection extends Connection
         return parent::delete($tableName, $identifier, $types);
     }
 
+    /**
+     * {@inheritDoc}
+     */
+    public function close()
+    {
+        unset($this->connections['master']);
+        unset($this->connections['slave']);
+
+        parent::close();
+    }
+
     /**
      * {@inheritDoc}
      */