java: discard the IPv6 zone id when parsing addresses

Reviewer: @vaterlaus

Zone IDs are used in link-local addresses to specify the interface name or 
number (RFC 4007). The InetSocketAddress class includes a zone id in the
output of getHostString() for link-local addresses. This change ignores the
zone id instead of raising an exception.

This fix is kind of a hack, better suggestions welcome.