lib, zebra: Fix vrf new hook callback.

lib, zebra: Fix vrf new hook callback.

This commit fixes two issues:

1) The creation of a new vrf from the cli was not calling the vrf_create hook.
This is fixed.

2) The zebra_vrf_delete callback was deleting interface information that
belonged to vrf not zvrf.  Remove the code as that it was not it's job
to do so.

Ticket: CM-10100
Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
Reviewed-by: Daniel Walton <dwalton@cumulusnetworks.com>