It is not possible to reliably detect what the type for an image should
be in the metadata. This commit adds an option for user to explicitly
provide it.
It can only be configured on the specific image, not globally.
Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>
(cherry picked from commit cd2ae81e3c63316997b9617ff2e30e3148af14f2)