switch Bugzilla to zirconium

this switches bugs, bugzilla, and bug-attachment
CNAMEs over from kaulen (old Bugzilla server) to
zirconium (new Bugzilla server)

in preparation for the upcoming migration

do not merge until Andre_/Daniel +1 it
and the maintenance window has been announced

Change-Id: Ic4f73eea19f994e988a2b77b9efc558822ffc64b