ipv6: Make sockopt IPV6_TCLASS behave like IP_TOS
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2172062
setsockopt(IP_TOS) on IPv4 sockets had two behaviors that were not
mirrored to setsockopt(IPV6_TCLASS) for IPv6 sockets: it prevented
setting the ECN bits on TCP sockets via TOS and it called sk_dst_reset()
when TOS was changed. We now mirror both behaviors to IPv6 sockets.
Signed-off-by: Felix Maurer fmaurer@redhat.com