Check if custom swarm controllers are needed

[oleschwen]

To reduce future documentation, maintenance, and test efforts, it would be helpful to use the NVFlare swarm client and server controller classes instead of our custom ones, which mainly implement additional exception logging. We should investigate which changes are really necessary and how/where to best implement them.

AC:

• decided if any changes to NVFlare controller classes need to be kept
• verified that training with NVFlare controller classes works in test setup
• verified that training with NVFlare controller classes works in ODELIA setup

[oleschwen]

Test runs with original controller classes and two and five client nodes via VPN throttled to 30 Mbit/s successful.
Test with five client nodes via production VPN in progress.