Fix LoS display in Autopilot/LoS-view

[Elblinator]

Current behaviour:
The current speaker can (visually) be behind the speaker before them

Reproduction:

1. Activate interposed question
2. Navigate to a LoS
3. Put speaker A on the LoS and start their contribution
4. put an interposed question on the LoS
5. start and stop the interposed question
6. (note: speaker A is currently paused)
7. put speaker B on the LoS
8. start speaker B
9. -> speaker A stays (in accent colour without mic) and speaker B is not visible
10. stop speaker A
11. speaker B is now visible with mic

Wanted behaviour:
If a new parent speaker is started then the old parent speaker should be moved into the Last Speakers-list

[bastianjoel]

Currently paused speakers won't get stopped if a new speaker is started.