Fix #12: Avoid duplicate package errors by virtualising them

If you set up both the server and client on the same RedHat machine,
you get a duplicate package error as they both depend on 'openldap'.
Making the package definitions for these virtual and then realizing
them immediately afterwards, we avoid that issue.

Note: fixes the 'ensure' value of the packages, but since this doesn't
seem to be available for a user to customise I'm not really sure why
it's there at the moment.