util: add nodejs context for bundle exec call

Bug 1030873
https://bugzilla.redhat.com/show_bug.cgi?id=1030873

NodeJS needs to be available for `bundle exec` call in `ruby/lib/util`
since it triggers asset compilation

See also:
* https://github.com/openshift/rails-example/commit/07d01120b308f415416a78d0bd7e9bd339d9ead3
* https://github.com/openshift/origin-server/commit/608c94857d26dd3242928c91fd30097b3775896b

Thanks to @jianlinliu for the tip.