Drop Bugzilla support

Summary:
Experimental code for Bugzilla support has been introduced,
to interact with some Bugzilla trackers.

Zed, Espace Win, Wikimedia now uses Phabricator.
There is no current plan to use it for FreeBSD.

So we can drop it.

This reverts commit 7d38eb85e6722f0a753a3544864ae3a224a4c410.

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D761