The cirros project has released new images, add them to our cache prior
to actually using them in the CI. We can remove the old images once the
migration is completed and not too many stable branches using the old
images are still active, but comparing the size of these in relation to
the total size of our images, the impact of this shouldn't be too large
in comparison to the benefit in CI stability.
Signed-off-by: Dr. Jens Harbott <harbott@osism.tech>
Change-Id: I6d6bcc0e9cfef059de70bbb19e4254e8d29d415b