juju 1.17.x cannot destroy a 1.16.5 azure environment

[Curtis Hovey]

CI has observed that juju 1.17.x cannot call destroy-environment
    $ juju destroy-environment --force test-cloud-azure
    ERROR empty image-stream in environment configuration

But doing this with 1.16.5 does succeed
    $ juju destroy-environment -e test-cloud-azure
    WARNING: this command will destroy the "test-cloud-azure" environment (type: azure)
    This includes all machines, services, data and other resources.

    Continue [y/N]? y

This may relate to the change that made image-stream available to all providers instead of just azure