Real time map view: respect end time of attempt

[saerdnaer]

When reusing the same tracker for different missions/robots (e.g. UPSail-Big and UPSail-Small both had tracker 7), tracker 7 will be shown on the real time map of both missions. The attempts are modelled correctly, but the end time is not honoured by the realtime view. Maybe this issue is also irrelevant due to issue #XX.