Remove jobcoordinator

JobCoordinator is no longer used in any of currently-active ODL projects. Its design is deeply flawed as it comes from an effort to paper over Genius architecture flaws (unsynchronized datastore access) and it suffers from composition problems as well as non-deterministic edge cases around cancelation – typical for single-usecase frameworks.

Rather than trying to fix it, just remove it so it does not confuse potential newcomers.