OVSDriver: use CFR when checking for overlapping kflows

Reviewer: @poolakiran

With the introduction of the meta_id match fields the OVS flow key is no
longer a superset of the OpenFlow match. This broke
ind_ovs_kflow_invalidate_overlap, which translated the kflow key into an
of_match and compared it with the of_match sent by the controller (which may
have had the meta_id fields un-wildcarded).

The fix, which should also be more performant, is to translate the of_match
and kflow key into a CFR.