totemip: Add support for sin6_scope_id

sin6_scope_id was not present in totemip structure making impossible to
use link-local ipv6 address.

Patch adds sin6_scope_id and changes convert/copy functions to use it
(formally also comparator functions should be changed, but it seems to
cause more harm and it is not really needed).

This makes corosync work with link-local addresses fine for both UDPU
and Knet transport as long as interface specification is used (so
fe80::xxxx:xxxx:xxxx:xxxx%eth0).

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Christine Caulfield <ccaulfie@redhat.com>