Scenario generator "broken" if ember-source is used

[Turbo87]

If the addon that is being tested has a dependency on ember-source then the scenario generator will work, but the scenarios generated (using bower) will not set ember-source to null which results in the Ember version being used to always be the one from ember-source.

In other words: All addons that use useVersionCompatibility and ember-source are not actually testing against the Ember versions that ember-try claims to test against, but are instead all testing against the same version of the original ember-try dependency.

This can be tested using e.g.

assert.equal(Ember.VERSION, '2.16.2');

which will pass on all generated scenarios if the ember-source version is 2.16.2.

This was discovered in mainmatter/ember-test-selectors#150

/cc @rwjblue @kategengler

[Turbo87]

released as v2.2.0