pimd: lookup nh using vrf_id we checked before

pimd: lookup nh using vrf_id we checked before

Update zclient_lookup_nexthop_once() to create the zapi
header using the vrf_id on the pim->vrf struct.

This is the one we do a check on a couple lines before, so
we should be using it when we actually create the header as
well.

Signed-off-by: Stephen Worley <sworley@cumulusnetworks.com>