container: inspect Id field instead of RepoDigests

container: inspect Id field instead of RepoDigests

When a container image managed by podman isn't tag anymore then the
RepoDigests field when inspecting the image doesn't return any value.
This is different from docker workflow and it breaks the ceph-ansible
container upgrade when collocated multiple services and using a non
fix container tag (like latest or 4).

$ podman images
REPOSITORY              TAG      IMAGE ID       CREATED        SIZE
docker.io/ceph/daemon   latest   680c9c0d38c3   8 days ago     957 MB
<none>                  <none>   011ee108bfc9   2 months ago   1.01 GB

$ podman inspect 680c9c0d38c3 | jq .[0].RepoDigests[0]
"docker.io/ceph/daemon@sha256:20cf789235e23ddaf38e109b391d1496bb88011239d16862c4c106d0e05fea9e"
$ podman inspect 011ee108bfc9 | jq .[0].RepoDigests[0]
null

Because this field returns "null" then the ansible task trying to
determine this value is failing

-----------------------------
fatal: [foo]: FAILED! =>
  msg: |-
    The task includes an option with an undefined variable. The error
    was: None has no element 0

    The error appears to be in
    'roles/ceph-container-common/tasks/fetch_image.yml': line 137,
    column 3, but may be elsewhere in the file depending on the exact
    syntax problem.

    The offending line appears to be:

    - name: set_fact ceph_osd_image_repodigest_before_pulling
      ^ here
-----------------------------

We don't have this behaviour with docker.

$ docker images
REPOSITORY              TAG      IMAGE ID       CREATED        SIZE
docker.io/ceph/daemon   latest   680c9c0d38c3   8 days ago     928 MB
docker.io/ceph/daemon   <none>   011ee108bfc9   2 months ago   986 MB

$ docker inspect 680c9c0d38c3 | jq .[0].RepoDigests[0]
"docker.io/ceph/daemon@sha256:45e6f28bb67c81b826acb64fad5c0da1cac3dffb41a88992fe4ca2be79575fa6"
$ docker inspect 011ee108bfc9 | jq .[0].RepoDigests[0]
"docker.io/ceph/daemon@sha256:b393a73309d72e43ca7d65cd3519036007947671e373eb59aa75a46185c52231"

Instead we should just get the Id field.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1844496
Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>
(cherry picked from commit cdb30bd125e5128328c3ccef15006acb23494d9c)