Fix the ctest javascript coverage report.
Fix the ctest javascript coverage report.

Tell nyc where we stored the coverage data so the test passes.  With
this change, ctest successfully passes locally.  Without it, it fails.

RafaelPalomar/girder,jbeezley/girder,girder/girder,jbeezley/girder,girder/girder,manthey/girder,Kitware/girder,RafaelPalomar/girder,jbeezley/girder,RafaelPalomar/girder,girder/girder,jbeezley/girder,manthey/girder,manthey/girder,Kitware/girder,RafaelPalomar/girder,Kitware/girder,RafaelPalomar/girder,girder/girder,manthey/girder,Kitware/girder