[sepia] teuthology-dispatcher is live

Hello folks, this past summer Shraddha Agrawal implemented a new way for teuthology to run tests - a single process, teuthloogy-dispatcher, locking and then running jobs, rather than a bunch of workers competing for locks [0]. Since there's a single dispatcher for each queue, jobs are run in strict priority order. This also enables a couple improvements to the test experience: 1) jobs may require more nodes - since only one job is locking at a time, they cannot be starved of available nodes 2) dead jobs will have full logs - jobs that hit the max_job_time (12 hours in sepia) will have full ceph logs and coredumps collected as usual - this should help quite a bit with stabilizing pacific For more details, check out the PR [1]. This is now running all the queues in the sepia lab - let us know if you run into any bugs! And thanks to Shraddha for her hard work on this! Josh [0] https://ceph.io/gsoc-2020/#teuthology-scheduling%20Improvements [1] https://github.com/ceph/teuthology/pull/1546