Make sure that the IB invalid pkey (0x0000 or 0x8000) isn't used for
child devices.

Also, make sure to always set the full membership bit for the pkey of
devices created by rtnl link ops.
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>