rds: IB active bonding IPv6 changes

rds: IB active bonding IPv6 changes

For IPv6, each interface can be associated with many addresses.  This
is handled by having an array of struct rds_ib_port_addr in each
struct rds_ib_port.  This new struct is only used for storing an IPv6
address to minimize code changes and is separate from struct
rds_ib_alias.  Note that address alias is obsolete and does not apply
to IPv6 address.  All the failover event handling code stays the same
except that IPv6 addresses are also moved.

Orabug: 25410192

Signed-off-by: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>