synchronized void release(int port) {
            if (port < first || port > last) {
                throw new RuntimeException("trying to release port outside valid range " + port);
            }
            if (!takenPorts.contains(port)) {
                throw new RuntimeException("trying to release port never acquired " + port);
            }
            takenPorts.remove(port);
            freePorts.push(port);
            notify();
        }
Allocates port ranges for all configserver tests.

@author Ulf Lilleengen
configserver/src/test/java/com/yahoo/vespa/config/server/PortRangeAllocator.java