Fix failing lightgbm test

[kxk302]

To reproduce the problem, run the following command:

planemo test --docker ./tools/sklearn/lightgbm.xml

Standard error:

Using TensorFlow backend.
/usr/local/lib/python3.6/site-packages/sklearn/externals/joblib/__init__.py:15: DeprecationWarning: sklearn.externals.joblib is deprecated in 0.21 and will be removed in 0.23. Please import this functionality directly from joblib, which can be installed with: pip install joblib. If this warning is raised when loading pickled models, you may need to re-serialize those models with scikit-learn 0.21+.
  warnings.warn(msg, category=DeprecationWarning)
/private/var/folders/pk/jwrvp5115zg81729h2x46f080000gn/T/tmp61d_ecjt/job_working_directory/000/6/tool_script.sh: line 22:    22 Segmentation fault      python '/private/var/folders/pk/jwrvp5115zg81729h2x46f080000gn/T/tmp61d_ecjt/job_working_directory/000/6/configs/tmpjwha3aqz' '/private/var/folders/pk/jwrvp5115zg81729h2x46f080000gn/T/tmp61d_ecjt/job_working_directory/000/6/configs/tmpemmo1kdd'

I ran the test in the PDB debugger inside the container (Per @bgruening's suggestion, had to add a long sleep statement to keep the container alive, then copied the necessary files over to run the same test again with sleep statement removed). However, the failure seems to happen in C code, hence, pdb has no useful info. Might have to debug it in gdb.

Commenting out the test for now as its blocking the release of the new version of galaxytools.