Fixed bugs in face_buffer.cpp.  Now use commDimPartitioned instead of commDim to determine whether to performance communication.  This has the effect that all functionality remains with QMP 2.3.1, and it is compatible with the internal QMP build (though comms partitioning does not work).
Merge branch '0.5.1-devel' of github.com:lattice/quda into 0.5.1-devel