Revert "Create system users for OpenStack components"

This reverts commit 37e819299b3f54641474289d93a0821e4d896ecf.
Revert "Avoid creating /nonexistent on compute nodes too"

This reverts commit 7014256c49d6c55c3e828782576f57c1b434cd1a.
Remove duplicate definition of nova user.
Merge pull request #181 from blueboxgroup/revert-system-users

Revert system users