This test has a failure that's happening only occassionally and not
very reproducibly. Print out the allocation status on test failure so
that we can do some post-mortum debugging of the test on nightly.
* Wait longer for node to go down in disconnected clients test.
The existing helper only waits 10s, but there's a jitter on heartbeats
that we need to account for. Wait for 30s for node to go down to give
us plenty of room
* Port disconnected clients to stdlib-style test
This test exercises the behavior of clients that become disconnected
and have their allocations replaced. Future test cases will exercise
the `max_client_disconnect` field on the job spec.
