When joining an IPoIB multicast group, use the same rate as in the
broadcast group.  Otherwise, if the RDMA CM creates this group before
IPoIB does, it might get a different rate.  This will cause IPoIB to
fail joining to the same group later on, because IPoIB uses strict
rate selection.
Signed-off-by: Yossi Etigin <yosefe@voltaire.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>