Fixed ev3dev.py to detecte motors at either /sys/class/tacho-motor/motor...

I have modified ev3dev.py to search both possible paths for the motors: /sys/class/tacho-motor/motor*/ or /sys/class/tacho-motor/tacho-motor*/.  This should be tested to make sure I got it right for the /sys/class/tacho-motor/motor*/ case but it is simple enough it should work without issue.  Although the new standard is for it to be at /sys/class /tacho-motor/motor*/ I would suggest using the more robust option of checking both possibilities.