Change in IPv4 versus IPv6 picking algorithm

When https://issues.jboss.org/browse/JGRP-2305 was implemented, IPv4 was favored unless java.net.preferIPv6Addresses was set.

However, this makes the following case fail: no java.net.preferXXX option is set and the configuration contains one or more IPv6 addresses, e.g. UDP bind_addr="::1".

This will fail, as the new algorithm sets the stack type as IPv4 (it works when java.net.preferIPv6Addresses is set).

Change:

• Look at all IP addresses in a configuration
• If all addresses are IPv6 and the stack type is IPv4 (and IPv6 is available) -> switch to IPv6 as stack type
• If all addresses are IPv4 and the stack type is IPv6 (and IPv4 is available) -> switch to IPv4 stack type