Race condition when updating documents when multiple stages are handling documents at the same time

[ssimon]

Using the SetStaticActionStage and at the same time running other stages, the status is not always updated.

Even though the document is fetched and touched by the SetStaticActionStage, the action is not changed.

[ssimon]

Possible reason: SerializationUtils - If a ConcurrentModificationException occurs, The method will retry with the same object again. If the object was changed (and it is since we got a ConcurrentModificationException?) these changes are overwritten.

[ssimon]

Applies to all fields, not only the action

[ssimon]

Only seems to be present when multiple CPU cores are present one the machine

[laserval]

Related to #299 and #142