Add a new network_clean_remove_all_ttcn3 function and use it in the fr related testsuites to ensure no network is running before the test starts. We just had the situation where the network link between gtp0-deb10fr (where these testsuites run exclusively, and only one at a time) and the jenkins host went down. And so the clean up trap apparently did not run and starting a new test fails as the old network still exists and has the network devices attached.
