Broken ember-source version check in nested addons

I think we have the same kind of bug [here](https://github.com/ember-cli/ember-cli-htmlbars/blob/d92706bc22c36094b7c5fd0607a5aa1675a867a5/lib/ember-addon-main.js#L173) as we did in [ember-cli-babel](https://github.com/babel/ember-cli-babel/pull/396).

It needs to check the ember-source version of the top-level project, not the parent package.