Allow status of tasks to be returned when getting an instance

[simonvane]

What would you like to be added:
Provide a way to get the status of tasks in an instance.

Why is this needed:
It would be helpful to be able to see what tasks are in progress when a plan is running or what tasks have failed if a plan fails. This would help with understanding progress and understanding why a plan had failed if there are multiple tasks in a step.

Perhaps this could be an additional flag to avoid too much noise, but on the other hand, if we are accessing the instance using the k8s api we want to get the tasks back so we can report the reason for failure.