Fix npm 3 build failure in phantomjs task
Fix npm 3 build failure in phantomjs task

npm v3.0+ by default dedupes node modules and stores them in a flat
tree, which means the hardcoded path to the location.js will no longer
be nested under the karma-phantomjs-launcher module.

This fixes issue #2999.

grafana/grafana,grafana/grafana,grafana/grafana,grafana/grafana,grafana/grafana,grafana/grafana,grafana/grafana