BUG: Fix OtsuThresholdImageFilterTest

Based on discussion during May 14 Slicer developer hangout, the test
failure was due to the transition to ITKv4.

The update of the baseline has been done with the following command:

cp /home/jchris/Projects/Slicer-TR-Superbuild-Release/Slicer-build/Testing/Temporary/OtsuThresholdImageFilterTest.raw.gz /home/jchris/Projects/Slicer-TR/Modules/CLI/OtsuThresholdImageFilter/Data/Baseline/

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22000 3bd1e089-480b-0410-8dfb-8563597acbee