Ensure `Ember.Test.adapter` is reset after `qunitModuleFor` tests.
Ensure `Ember.Test.adapter` is reset after `qunitModuleFor` tests.

Leaving a `Ember.Test.adapter` in place means the tests run
inconsistently depending on if a `qunitModuleFor` test had previously
been ran.

switchfly/ember-test-helpers,switchfly/ember-test-helpers