Clean up some service profiler behavior in Conduit futures
Correct two minor Conduit future issues:
- FutureAgent shows up in the trace log as "<mystery>". Since it isn't doing anything useful, solve the mystery and drop it from the log.
- Simply the ConduitFuture code for interacting with the service profiler now that a more structured integration is available.
Test Plan: Ran "arc branches --trace", saw conduit calls and no more "<mystery>" clutter.
Differential Revision: https://secure.phabricator.com/D21388