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