A list of Redis instances in the project in the specified
location, or across all locations.
If the ``location_id`` in the parent field of the request is
"-", all regions available to the project are queried, and
the results aggregated. If in such an aggregated query a
location is unavailable, a placeholder Redis entry is
included in the response with the ``name`` field set to a
value of the form
and the ``status`` field set to ERROR and ``status_message``
field set to "location not available for ListInstances".
Token to retrieve the next page of results,
or empty if there are no more results in the
Locations that could not be reached.