Flush recv_buffer on cancellation

If asyncio.wait_for is cancelled by the caller we need to clean up
the recv_buffer as well.

Author: jameshilliard

pymodbus/transaction/transaction.py

@@ -153,6 +153,9 @@ async def execute(self, no_response_expected: bool, request: ModbusPDU) -> Modbu
                     return response
                 except asyncio.exceptions.TimeoutError:
                     count_retries += 1
+                except asyncio.exceptions.CancelledError:
+                    self.recv_buffer = b""
+                    raise
             if self.count_until_disconnect < 0:
                 self.connection_lost(asyncio.TimeoutError("Server not responding"))
                 raise ModbusIOException(