RDO registry denies images uploads

[Gabriele Cerami]

This is a recurring bug, opening to keep track of its evolution

After building and tagging containers images in rdoproject, trying to upload
them to rdo registry, fails with the error

INFO:kolla.image.build.neutron-base:Trying to push the image
ERROR:kolla.image.build.neutron-base:unauthorized: authentication required

Last occurence of this bug is shown in

https://review.rdoproject.org/jenkins/job/periodic-tripleo-centos-7-pike-containers-build/59/consoleFull

This time it happened only with neutron-base image
Previously it happened with every image.

David Simard already attempted to fix this in several occasions, and he makes it work for a while.