
ensure 4 spaces indentation is used everywhere. Change-Id: Ieb48faacb4c96b7b358771d70c17f2f22d0354f4
Provide yum specific image building glue.
RHEL/Fedora/CentOS and other yum based distributions need specific yum customizations.
Customizations include caching of downloaded yum packages outside of the build chroot so that they can be reused by subsequent image builds. The cache increases image building speed when building multiple images, especially on slow connections. This is more effective than using an HTTP proxy as a yum cache since the same rpm from different mirrors is often requested.