manage-offline-container-images.sh

When running the script, I faced the following error but it was
difficult to know the root problem due to lack of error handling.

  docker tag" requires exactly 2 arguments.
  See 'docker tag --help'.

  Usage:  docker tag SOURCE_IMAGE[:TAG] TARGET_IMAGE[:TAG]

  Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE

To investigate such errors easily, this adds an error handling.