The default executor does not exit if a single task pod fails.

If a task group has a single task and it exits with a non-zero exit code, the default executor does not commit suicide.

This mostly happens due to the fact that we invoke shutdown() in waited() when we notice the termination of a single container here: https://github.com/apache/mesos/blob/master/src/launcher/default_executor.cpp#L666

but then we return early here after executing all the kill calls: https://github.com/apache/mesos/blob/master/src/launcher/default_executor.cpp#L751

However, when there is just one task in the task group, this won't result in __shutdown being called ever leading to the executor committing suicide.