Fixed language around upgrading with multiple roles on single node

It's not actually possible to have the "master and console on the same
node" without doing an all-in-one installation - the original language
makes it sound like you can have master and console on one node, and
PuppetDB on another. Not the case.
Merge pull request #301 from zacharyalexstern/fix_misleading_upgrade_example

Fixed language around upgrading with multiple roles on single node