Bug 964527 - Run npm install as a separate step, r=gaye
Bug 964527 - Run npm install as a separate step, r=gaye

--HG--
branch : production
extra : rebase_source : f466be651afa5b9984fa0694b62aab57337edddb

kartikgupta0909/mozilla-mozharness,simar7/build-mozharness,kartikgupta0909/build-mozharness,armenzg/build-mozharness,mrrrgn/build-mozharness,walac/build-mozharness,kartikgupta0909/gittest,kartikgupta0909/mozilla-mozharness,armenzg/build-mozharness,kartikgupta0909/gittest,kartikgupta0909/build-mozharness,walac/build-mozharness,lissyx/build-mozharness,mozilla/build-mozharness,lissyx/build-mozharness,simar7/build-mozharness,mozilla/build-mozharness,escapewindow/mozharness,mrrrgn/build-mozharness,escapewindow/mozharness