Refactor PAM configuration
    
    The cracklib module was removed from Tumbleweed, causing errors with the
    Salt installed configuration files referencing it.
    Use pam-config instead of "manually" managed files - this avoids breakage
    when PAM modules change.
    
    Signed-off-by: Georg Pfuetzenreuter <georg.pfuetzenreuter@suse.com>