BUG: GDCM IO: reset internal variables
BUG: GDCM IO: reset internal variables

It is safer to reset several variables on InternalReadImageInformation,
because a user can re-use the IO.

richardbeare/ITK,InsightSoftwareConsortium/ITK,hjmjohnson/ITK,BRAINSia/ITK,thewtex/ITK,Kitware/ITK,Kitware/ITK,hjmjohnson/ITK,thewtex/ITK,thewtex/ITK,hjmjohnson/ITK,InsightSoftwareConsortium/ITK,hjmjohnson/ITK,InsightSoftwareConsortium/ITK,richardbeare/ITK,Kitware/ITK,BRAINSia/ITK,thewtex/ITK,BRAINSia/ITK,InsightSoftwareConsortium/ITK,BRAINSia/ITK,Kitware/ITK,thewtex/ITK,richardbeare/ITK,InsightSoftwareConsortium/ITK,thewtex/ITK,BRAINSia/ITK,richardbeare/ITK,Kitware/ITK,BRAINSia/ITK,Kitware/ITK,hjmjohnson/ITK,BRAINSia/ITK,InsightSoftwareConsortium/ITK,thewtex/ITK,richardbeare/ITK,richardbeare/ITK,richardbeare/ITK,hjmjohnson/ITK,hjmjohnson/ITK,InsightSoftwareConsortium/ITK,Kitware/ITK