image_uploader: raise an error when podman pull fails
image_uploader: raise an error when podman pull fails

It's not obvious when a podman pull fails multiple times in a row, it
was displayed as INFO, and now it will be shown at ERROR debug level for
more visibility when something is wrong with the image.

Change-Id: Ia616ae22ebf6f4c562ef7dc95ed62ada511951b4

openstack/tripleo-common,openstack/tripleo-common