ci: switch all non-released distros to be non-gating

ci: switch all non-released distros to be non-gating

The non-released distros have reasonably frequent package installation
failures that can last for days at a time. This makes them unsuitable
for use as gating CI jobs.

This ensures all of the jobs in Debian Sid, Fedora Rawhide, openSUSE
Tumbleweed and FreeBSD Current are marked "allow-failure: true".

This means the jobs still run, but any failure will not be considered
fatal to the pipeline.

Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>