Do not add pkgset_koji_builds to modules, but only to pkgset_koji_tag tags.
    
    Also remove the useless listTaggedRPMs call which has been used *only*
    to catch the very rare error which happened from time to time when
    we used PDC in Pungi few years ago. This rare error is not relevant
    anymore now.
    
    Signed-off-by: Jan Kaluza <jkaluza@redhat.com>