- Fixed error recovery

[lmartorella]

Hi,
I've found an issue in cleaning up the RTU module state, that happens in one of the following cases of incoming packet:

• a CRC error is detected (e.g. malformed packet or transmission error due to noisy line);
• a custom cbRaw callback is installed and a EX_PASSTHROUGH is returned when the frame was not valid, but the CRC was ok;

In these cases, the state of the receiver is not correctly reset, and it is impossible to send new packets (e.g. the send() always returns false) until the timeout elapsed. This is because the cleanup() function only acts after MODBUSRTU_TIMEOUT_US timeout.

Setting _slaveId = 0 at the end of the task() fixes the issue.
It is also probably better to get rid of the goto used in the task() function and linting it.

Thanks!
L