BUG: checkMesh - cellZone bounding box incorrect

angledDuct explicit tutorial in develop branch

• gives incorrect min bounding box limit

    CellZone            Cells    Points   BoundingBox  
    inlet               6000     7056     (  -0.15 0 -0.025) (0 0.0353553 0.025)
    porosity            8000     15876    (  -0.15 0 -0.025) (0.0707107 0.106066 0.025)
    outlet              8000     24696    (  -0.15 0 -0.025) (0.141421 0.176777 0.025)