Version: 1.0.1

Current state

If I have a nodejs installation configured to not install any global modules, it will not be respected.
The command will anyway execute with "npm install -g" which is not valid.

$ /Users/<user>/.jenkins/tools/jenkins.plugins.nodejs.tools.NodeJSInstallation/NodeJS_6.9.4/bin/npm install -g 
npm ERR! Usage:
npm ERR!     npm cache add <tarball-url>
npm ERR!     npm cache add <pkg>@<ver>
npm ERR!     npm cache add <tarball>
npm ERR!     npm cache add <folder>
npm ERR! 

Expected behavior

The command "npm install -g " will not run if there is no configuration for global modules.