No tags repo removal for AWS ECR

[romasku]

In AWS, a repo can exist after the last tag was removed. This leads to "unremovable" images in neuro image ls. To overcome this problem, this fix was introduced, but it can lead to problems if the user tries to list tags before they upload the first image, as it will drop repo.
The solution is to add a special endpoint to remove the repo and use it in the client when neuro image rm was called for AWS ECR repo.