Fix windshaft install on vagrant boxes

Provisioning a fresh vagrant box from scratch was failing at the
windshaft stage. Running npm install manually resolved the problem, so
this simulates the login process when running the windshaft install from
the provision script. I was able to successfully provision a fresh
vagrant box with this change.
Merge pull request #98 from WorldBank-Transport/feature/fix-blank-provision

Fix windshaft install on fresh vagrant boxes