Yast new installer changes

- added `yast2-ldap-client`, `yast2-pam` and `yast2-security` to the root
  image (needed to write the user configuration in the 1st stage)
- `yast2-runlevel` has been replaced by `yast2-services-manager`
Merge pull request #7 from lslezak/new_installer_changes

Yast new installer changes