filter retired/blacklisted cntrs - fedcontainer_rc
Refactoring the container release candidate code a bit and include
a blacklist functionality for images that should never have existed
in the first place (mostly due to growing pains in the Atomic WG
around container best practices and guidelines, we likely won't
need this in the future). Also add filtering for Retired packages.
One thing to note is that right now this is querying pkgdb and
datagrepper but in the future it should be asking koji about
the list of containers in the fXX-docker-pending tag. Unfortunately
at this time we don't have the ingress point (CI/CD test pipeline)
to trigger an action to move containers into that tag. We will
switch to that ASAP but this will get us moving for the time being.
Signed-off-by: Adam Miller <maxamillion@fedoraproject.org>