Fix os detection for CentOS
Fix aptitude commands for long package names

Use "disable-columns" option when running aptitude search to find
packages with long names.

Use aptitude --disable-columns when verifying packages are installed.
Only mirror permissions to state-root if needed

When mirroring permissions, only adjust the permissions if they do not
already match.  This is to prevent chmod, chown and chgrp errors.
Refactor state-root script into functions
Add :no-deref option to symbolic-link
Fix action :sudo-user with a :no-sudo admin user

When using :no-sudo in the admin user, ensure that an explicit
:sudo-user action option is honoured.

Fixes #300