Add retry logic to retrieve_latest_base_ami request

[robrap]

AC:

• Auto retry the request in tubular retrieve_latest_base_ami.

Notes:

The request here sometimes fails: https://github.com/openedx/tubular/blob/master/tubular/scripts/retrieve_latest_base_ami.py#L83.

Retry logic could be added by refactoring out that call to a new decorated method using:

@backoff.on_exception(
    backoff.expo,
    requests.exceptions.RequestException,
    max_tries=5, jitter=backoff.random_jitter, on_backoff=_backoff_logger,
)