Preserve pam-config on Tumbleweed
    
    If removed, it gets re-installed on distribution upgrades (pulled
    in through some unknown package) and replaces the custom PAM
    iconfiguration. Hence leave it installed only replace the symlinks
    - as per pam-config(8).
    
    Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>