Fix lookup of catalogs in consolidate so that multiple catalogs could be used (e.g. cmip6 AND cmip5)

[agstephens]

See code here:

https://github.com/roocs/daops/blob/master/daops/utils/consolidate.py#L131-L133

Need to move the catalog lookup to work on a per-dataset level. (Could cache them all in an object before looping through).