1. rootfs.path set, -t not set: rootfs.path is rootfs path
2. rootfs.path set, -t set: change template default path to rootfs path
3. rootfs.path not set, -t set: template default path is rootfs path
4. rootfs.path not set, -t not set: error
5. rootfs.path set but cannot access: error
Signed-off-by: Sheng Yong <shyodx@gmail.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>