Close leaked selector in version check (#1425)

Author: dpkp

kafka/conn.py

@@ -928,6 +928,7 @@ def connect():
                 for response, future in self.recv():
                     future.success(response)
                 selector.select(1)
+            selector.close()
 
             if f.succeeded():
                 if isinstance(request, ApiVersionRequest[0]):