Delete sporadic failing spec that tests rufus.
Delete more sporadic failing specs that test rufus.

These specs test that what we put in rufus based on the server's role will produce the associated queue rows.
This, if useful, can be done without needing to test rufus internals.
Remove a sporadic failing spec.

It's useful to verify that a schedule's last_run_on is updated only on completion and not on queueing of the scheduled work.

Unfortunately, this test relies on the underlying implementation of rufus.

If this test is useful to have, we'll have to reorganize the code so we can test just queueing in isolation.
Remove RufusSchedulerHelper now that it's unused.
Merge pull request #413 from jrafanie/delete_brittle_specs

Delete brittle specs