bugzilla: disable "quick" sync in favor of a full sync
    
    The standard "quick" sync takes one or two orders of magnitude longer than a
    full sync, and often times out. It seems that while the timestamp optimizations
    were helpful with older Bugzilla versions, with Bugzilla5 they are taking
    extremely long to evaluate. It seems much better to always do a "full" sync
    instead.
    
    If we don't see any negative consequences, let's remove the quick sync code
    completely.
    
    Merges: https://pagure.io/fedora-qa/blockerbugs/pull-request/183
    Related: https://pagure.io/fedora-qa/blockerbugs/issue/184