GTiff: to make Python bindings happy, avoid emitting CE_Failure errors due to libtiff errors when we still manage to open the file (#5616)

git-svn-id: https://svn.osgeo.org/gdal/trunk@27589 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' into trunk_with_coverage