Store document uuids before executing callbacks in RunRouter

[jklynch]

When method RunRouter.descriptor executes a callback which raises an exception, the RunRouter._descriptor_to_start and RunRouter._start_to_descriptors dictionaries are not updated starting on this line. This can cause a dictionary lookup failure at a later time when, for example, an event document is processed which references the offending descriptor document.

Expected Behavior

The offending descriptor should be used to update RunRouter._start_to_descriptors and RunRouter._descriptor_to_start.

Current Behavior

The dictionaries are not updated if a callback raises an exception.

Possible Solution

Update the dictionaries before executing callbacks.