Mesos may report completed task as running in the state.

When the following steps occur:
1) A graceful shutdown is initiated on the agent (i.e. SIGUSR1 or /master/machine/down).
2) The executor is sent a kill, and the agent counts down on executor_shutdown_grace_period.
3) The executor exits, before all terminal status updates reach the agent. This is more likely if executor_shutdown_grace_period passes.

This results in a completed executor, with non-terminal tasks (according to status updates).

This would produce a confusing report where completed tasks are still TASK_RUNNING.