Support JGroups fix start port and port offset in the server for FD_SOCK

As the server parameter '-o' can add a port offset to the jgroups.bind.port the FD_SOCK port is not affected. Also the port is configured as random which is not ideal.

The legacy server used the socket-bindings to use a fixed start port (udp-fd=54200 and tcp-fd=57800) and incremented the port if the port-offset was used.

This should be similar for the new jgroups configuration.