TEST: Some tests fail if ITK_GLOBAL_DEFAULT_NUMBER_OF_THREADS==6

Some boundary conditions occur when running on a 6-cores cpu instead of a 4, 8 or 12 cores. This happens for apTvSeSegmentationMeanshiftVector and bfTvMeanShiftSmoothingImageFilterOptim

~/src/otb/build$ ITK_GLOBAL_DEFAULT_NUMBER_OF_THREADS=6 ctest -R apTvSeSegmentationMeanshiftVector
1/1 Test #272: apTvSeSegmentationMeanshiftVector ...***Failed    1.40 sec
~/src/otb/build$ ITK_GLOBAL_DEFAULT_NUMBER_OF_THREADS=4 ctest -R apTvSeSegmentationMeanshiftVector
1/1 Test #272: apTvSeSegmentationMeanshiftVector ...   Passed    1.30 sec

Edited Oct 21, 2019 by guillaume pernot