BUG: Comparison of Darcy's law with porousSimpleFoam

I guess there is a problem with solving flow through a porous medium. A comparison of porousSimpleFoam with Darcy's law fails and the computed pressure drop is too low in comparison to theory. It seems that there is always one discretization cell missing. I have attached a report to show the issue openFoam_bugReport.pdf

The problem was already reported here: https://www.cfd-online.com/Forums/openfoam-solving/183947-poroussimplefoam-comparison-darcys-law.html

The test case is attached Darcy_test.zip

I am using version v1606+ with a virtual machine on Windows 7.

## Reattaching the author to the issue ticket: @sepp.zell ##