add yum plugin to repatch rootfs on yum update

oracle-template: Split patching rootfs vs one time setup into separate
shell functions so the template can be run with --patch.

oracle-template: Update to install the yum plugin and itself (as lxc-patch)
into a container. The plugin just runs lxc-patch --patch <path> so it is
fairly generic, but in this case it is running a copy of the template inside
the container.

Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>