As a follow-on to I728d38daf9a953a64364689da0648c9339a27693, use the
per-release distro path for the mirror.
Change-Id: Ib75904c801a7de4a914db55ca70b192d586461cd
Our .zuul.yaml file has grown quite large. Try to make this more
manageable by splitting it into zuul.d/ directory with jobs organized by
function.
Change-Id: I0739eb1e2bc64dcacebf92e25503f67302f7c882