BUG: snappyHexMesh: findCellZoneTopo was copying same value but still setting

changed flag which caused infinite while loop. Background info:
- findCellZoneTopo tries to find for all named surface intersections
which side of the face is in the faceZone
- i.e. it tries to make the cellZone consistent with the faceZone
(to fix small problems)
- this had some logic to assign the neighbour cellZone to the owner cellZone
- which didn't check for the neighbour being the same value as the owner
- but still set a 'changed' flag which caused the loop to never end.