s3:lib/util_sock: listen on IPv6 addresses with IPV6_ONLY (bug #7383)
This avoids getting IPv4 addresses as mapped IPv6 addresses
(e.g. ::ffff:192.168.0.1).
Before the bahavior was inconsistent between operating system
and distributions. Some system have IPV6_ONLY as default.
Now we consistently get AF_INET for IPv4 addresses and AF_INET6
for IPv6 addresses.
It also makes it possible to listen only on IPv6 now
as "::" doesn't imply "0.0.0.0" anymore. Which also
avoids confusing log messages that we were not able to
bind to "0.0.0.0".
metze