net: setsockopt: fix IPV6_UNICAST_IF option for connected sockets

Change the behaviour of ip6_datagram_connect to consider the interface
set by the IPV6_UNICAST_IF socket option, similarly to udpv6_sendmsg.

This change is the IPv6 counterpart of the fix for IP_UNICAST_IF.
The tests introduced by that patch showed that the incorrect
behavior is present in IPv6 as well.
This patch fixes the broken test.

Reported-by: kernel test robot <oliver.sang@intel.com>
Link: https://lore.kernel.org/r/202210062117.c7eef1a3-oliver.sang@intel.com


Fixes: 0e4d3547 ("net-next: Fix IP_UNICAST_IF option behavior for connected sockets")

Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>