Update mapping from RT to VRF table.

def update_vrf_table_links(self, vrf_table, new_imp_rts,
                               removed_imp_rts):
        """Update mapping from RT to VRF table."""
        assert vrf_table
        if new_imp_rts:
            self._link_vrf_table(vrf_table, new_imp_rts)
        if removed_imp_rts:
            self._remove_links_to_vrf_table_for_rts(vrf_table,
                                                    removed_imp_rts)