Make sure the IPv6 scope ID gets zeroed when exchanging CMA messages in ibcore.
Else the IPv6 address matching might fail. This change adds support for both
embedded and non-embedded IPv6 scope IDs when passing a IPv6 link-local socket
address to RDMA. Prior to this change only global IPv6 addresses would work
with RDMA.

Sponsored by: Mellanox Technologies
MFC after: 1 week