py TSocket: Only disable socket.IPV6_V6ONLY when the family is AF_INET6

[derkuci]

The changes introduced in 916ae8b causes OSError when the socket is of IPv4 family. This can be verified by the code snippet below (at least on RHEL 8 and RHEL 9 with Python 3.9):

import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 0)

This will raise an exception OSError: [Errno 92] Protocol not available.

My fix is pretty simple: only set that IPv6 option when the socket family is IPv6.