some more robustness added to CAN reset

During watchdog testing, I produced a pretty harsh load for the lemcom, upping the rate of the beacon (which continues to use CAN). I had to do some heuristic improvements to double and triple check the rx/tx errors to make sure they are cleared out. However, there is such a bombardment of CAN requests that it doesn't stay cleared out for long, so my improvements only make it more robust, just not foolproof.