<nodejs cartridge> Fix npm link for SCL versions

npm link was being run in the system context instead of the SCL context
during install if an SCL version is chosen.

nodejs_context uses $OPENSHIFT_NODEJS_VERSION, but since this variable
is also set in the bin/install script, need to explicitly set the
variable to prevent errors with using nodejs_context in bin/install

Removing modules from the npm_global_module_list that do not exist in
the installed SCL package set.