Make OverlappingCouplingFunctor threadable
Make OverlappingCouplingFunctor threadable

This *particular* fix is probably efficient enough for use, but when we
fix #2334 we should change this to use (and get test coverage of) the
new GhostingFunctor::clone() API instead.

BalticPinguin/libmesh,BalticPinguin/libmesh,dschwen/libmesh,BalticPinguin/libmesh,roystgnr/libmesh,libMesh/libmesh,jwpeterson/libmesh,capitalaslash/libmesh,jwpeterson/libmesh,capitalaslash/libmesh,libMesh/libmesh,dschwen/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,BalticPinguin/libmesh,jwpeterson/libmesh,capitalaslash/libmesh,libMesh/libmesh,libMesh/libmesh,libMesh/libmesh,roystgnr/libmesh,capitalaslash/libmesh,roystgnr/libmesh,dschwen/libmesh,roystgnr/libmesh,dschwen/libmesh,roystgnr/libmesh,jwpeterson/libmesh,roystgnr/libmesh,roystgnr/libmesh,libMesh/libmesh,BalticPinguin/libmesh,dschwen/libmesh,libMesh/libmesh,dschwen/libmesh,jwpeterson/libmesh,dschwen/libmesh,BalticPinguin/libmesh,capitalaslash/libmesh,BalticPinguin/libmesh,BalticPinguin/libmesh,dschwen/libmesh,libMesh/libmesh,capitalaslash/libmesh,capitalaslash/libmesh,capitalaslash/libmesh,jwpeterson/libmesh,roystgnr/libmesh