Fix Container.image resolving the wrong image

[UditDewan]

Fixes #3144

What

Container.image splits the value it looks up on the first colon and keeps the second half:

image_id = self.attrs.get('ImageID', self.attrs['Image'])
if image_id is None:
    return None
return self.client.images.get(image_id.split(':')[1])

That is correct only when the value is a digest (sha256:<hex>). Daemons that don't report ImageID put an image name in Image instead, so busybox:latest gets split into latest, which is then looked up as an image ID:

docker.errors.ImageNotFound: 404 Client Error for
http+docker://localhost/v1.40/images/latest/json: Not Found
("failed to find image latest: latest: No such image")

The failure isn't always loud — if some unrelated image happens to be tagged latest, the wrong Image is returned silently.

There is a second, smaller bug on the same line: self.attrs['Image'] is the default argument to .get(), and Python evaluates it eagerly. A container whose attributes carry ImageID but no Image raises KeyError: 'Image' even though the ImageID needed to answer the call is right there.

How

Strip only the sha256: prefix and pass anything else through untouched. This matches how Image.short_id and Image.tag already discriminate these values, so no new parsing helper is introduced.

The requests sent for inputs that already worked are byte-for-byte unchanged — a sha256:-prefixed ImageID or Image still resolves to the same bare hex ID as before. Only the previously-broken name case changes behaviour. The Image lookup also moves to .get() so the eager-default KeyError goes away.

Testing

Three unit tests in tests/unit/models_containers_test.py covering name, digest, and neither-key-present. Against the current code they fail with exactly the reported symptoms:

E   AssertionError: expected call not found.
E   Expected: inspect_image('busybox:latest')
E     Actual: inspect_image('latest')

E   KeyError: 'Image'

Worth noting that the existing test_image passed only by accident: the fake API returns the same image for any name, so the bogus latest lookup went unnoticed. The added assertion pins the argument rather than just the result.

Full unit suite passes. Three unrelated failures (test_log_since_with_datetime, test_events_with_since_until, test_kwargs_from_env_no_cert_path) reproduce on a clean checkout of main on Windows/non-UTC and are tracked in #3335.