doc: remove leading / from python script args

On some (presumably older?) deployments of ZeroCloud, having the leading
slash was resulting in scripts failing--not only failing, but also
showing no output or errors.

Honestly, I have no idea what the root cause is. It doesn't seem to be
an issue on Zebra.

This issue was discovered during the discussion in this thread: https://groups.google.com/d/msg/zerovm/WbMWBsYdYRY/cROz8Xw8y5sJ