Adapt to post-3085 changes in pipe_base, removing ugly workaround.

This PR removes an ugly workaround in the HSC forced photometry task, made possible by the merge of a better solution from LSST on ticket https://dev.lsstcorp.org/trac/ticket/3085.

There's also a PR for pipe_base.

I'd merge this myself, but I'd prefer to wait until the integration tester is up and running again in case I made a stupid mistake.