(Docs) updated rabbitmq cli syntax and CLI permissions

I recently set up my first rabbitmq instance for mcollective purposes.  Looks like there have been some CLI syntax changes, and also permissions for the guest/guest to modify the new ``/mcollective`` vhost are not assigned automatically.

There is an alternative example which is of course to use the ``mcollective`` user with ``rabbitmqadmin`` throughout the examples. 

Thanks kindly.