use OSG pilot instead of custom tarball

[dsschult]

OSG has a working, and maintained, containerized HTCondor pilot at https://github.com/opensciencegrid/osgvo-docker-pilot.

To save us lots of duplicated effort, replace our custom HTCondor tarball with that.

As part of this, we'll also need to change to token-based auth, so likely other changes bundled in here.

This gets us compatibility with HTCondor >= 8.9, and closes #164, #115, #108, #82, and #1.