actions: ostree_deploy: allow to work without the image action
actions: ostree_deploy: allow to work without the image action

Allow to use rootdir directly if OStree should be prepared without
the image, i.e. packed to tarball.

Signed-off-by: Denis Pynkin <3fbf95ee68899518ee8799d35f88c8f7982aa936@collabora.com>

go-debos/debos,d4s/debos