This patch moves execCmd and friends to new commands module, so code not using
these can be ported to Python 3. More work is needed to make execCmd compatible
with Python 3, and we don't want to delay the work on other modules
that do not depend
on it, but import utils.
Since this change touches all sub systems in vdsm, subsystems maintainers
should review and *verify* that it does not break anything.
Please review and verify:
We are going to merge it on end of next week, so better check that it does not
break your code before that.