add_javascript_style_test: Ensure .jshintignore is considered for plugins
add_javascript_style_test: Ensure .jshintignore is considered for plugins

By setting the working directory to match input directory, this commit
allows .jshintignore located in the input directory to automatically be
found and used.

jcfr/girder,Xarthisius/girder,essamjoubori/girder,Kitware/girder,data-exp-lab/girder,essamjoubori/girder,RafaelPalomar/girder,manthey/girder,manthey/girder,jbeezley/girder,adsorensen/girder,data-exp-lab/girder,opadron/girder,kotfic/girder,msmolens/girder,jbeezley/girder,msmolens/girder,adsorensen/girder,kotfic/girder,msmolens/girder,sutartmelson/girder,chrismattmann/girder,Xarthisius/girder,Xarthisius/girder,kotfic/girder,jcfr/girder,adsorensen/girder,Kitware/girder,RafaelPalomar/girder,adsorensen/girder,girder/girder,jbeezley/girder,chrismattmann/girder,chrismattmann/girder,Xarthisius/girder,manthey/girder,opadron/girder,salamb/girder,opadron/girder,salamb/girder,msmolens/girder,opadron/girder,kotfic/girder,sutartmelson/girder,sutartmelson/girder,jbeezley/girder,Kitware/girder,manthey/girder,sutartmelson/girder,essamjoubori/girder,girder/girder,RafaelPalomar/girder,chrismattmann/girder,salamb/girder,kotfic/girder,girder/girder,data-exp-lab/girder,Xarthisius/girder,adsorensen/girder,RafaelPalomar/girder,RafaelPalomar/girder,jcfr/girder,girder/girder,data-exp-lab/girder,opadron/girder,essamjoubori/girder,data-exp-lab/girder,essamjoubori/girder,sutartmelson/girder,jcfr/girder,jcfr/girder,salamb/girder,salamb/girder,chrismattmann/girder,msmolens/girder,Kitware/girder