Motivation:
This fixes a bug that would result in an `io.netty.channel.unix.Errors$NativeIoException: connectx(..) failed: Address family not supported by protocol family` error.
This happens when the connecting socket is configured to use IPv6 but the address being connected to is IPv4.
This can occur because, for instance, Netty and `InetAddress.getLoopbackAddress()` have different preferences for IPv6 vs. IPv4.
Modification:
Pass the correct ipv6 or ipv4 flags to connectx, depending on whether the socket was created for AF_INET or AF_INET6, rather than relying on the IP version of the destination address.
Result:
No more issue with TCP FastOpen on MacOS when using addresses of the "wrong" IP version.
9eb4f0ee85