Convert cmdlib.py to use the logging module

Note that many uses of logger.Error were used in 1.2 for their
side-effect of logging to stderr, where the user will see the messages,
and not for having the entry in the log. As such, we need to go over and
review every use of logging.* and decide if it should use feedback_fn
instead of being a logging call.

Reviewed-by: imsnah