This is take two on #109. What's different this time is that we just
include *both* the primary and secondary `dl.fp.o` baseurls. The stack
knows how to handle this and just tries one before going to the next.
The baseurl doesn't apply equally across all basearchs, so let's go back
to using metalink for now. I think we could get what we want using
custom mirrorlists, though want to explore this space a bit more first.
This is prep for having `testing-devel` be the source of truth for all
the files other than the lockfile and manifest (see [1]). We just have
one `fedora.repo` file which contains all the repos we care about, but
only actually enable the appropriate ones for each stream independently.
In this case, once packages are tagged, `testing-devel` will just use
the `coreos-pool` repo.
[1] https://github.com/coreos/fedora-coreos-tracker/issues/204
Otherwise, we can hit different mirrors on each run. This is an issue in
our pipeline since it breaks our change detection. See:
https://github.com/coreos/fedora-coreos-pipeline/issues/85
There could be nicer ways to do this in the future. This will fix things
for now at least.
