BUG: Fix reading of DWI files. Fixes #3545

This commit fixes regression introduced by commit r22753 fixing issue #3511
that was preventing "vtkNRRDReader::CanReadFile" from returning the correct
value.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22801 3bd1e089-480b-0410-8dfb-8563597acbee
STYLE: Consistently report error in vtkMRMLNRRDStorageNode read/write method

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22802 3bd1e089-480b-0410-8dfb-8563597acbee