This was racy with the sleep, so the Compose file has been
tweaked to make it pass reliably.
Now, there's 3 services:
* `running` - sleeps forever
* `exit` - exits _successfully_ immediately
* depends on `running` started
* `fail` - exits _with error_ immediately
* depends on `exit` succeeding
Now, the test can ensure that the containers are all run/
started in the expected order the assertions will be reliable.
Before, it was possible for `fail` to run & exit before `exit`,
for example. The `running` service also ensures there's always
at least one other "running" container when we do an abort.
Signed-off-by: Milas Bowman <milas.bowman@docker.com>
36bf0c458b