When building images for another release or distro, we don't want to use
the host's repo directory but a specific ones.
We simply remove /etc/yum.repos.d from the default mounts and add a
--repo-dir argument that will be used to add the mount afterward.
Change-Id: I51d9fd25efcc94ff6a76cfe2f4bc5d45bbfc141d
(cherry picked from commit 4a6df27917)
015e022685