Replace while-loop in subexperiment script by do-while

The subexperiment script run_uc1-new.sh to run_uc4-new.sh all execute the following (or similiar) while-loop:

while test $(kubectl exec kafka-client -- bash -c "kafka-topics --zookeeper my-confluent-cp-zookeeper:2181 --list" | sed -n -E '/^(titan-.*|input|output|configuration)( - marked for deletion)?$/p' | wc -l) -gt 0
do
    kubectl exec kafka-client -- bash -c "kafka-topics --zookeeper my-confluent-cp-zookeeper:2181 --delete --topic 'input,output,configuration,titan-.*'"
    echo "Wait for topic deletion"
    sleep 5s
done

This but replaced by a do-while-loop in order to avoid the useless, time-intensive first check.

While this is a quite simple adjustment, it has to be sufficiently tested.