[BUGFIX beta] Route.send is unit testable

this.router doesn’t exist when unit testing
Ember.Route, and hence .send breaks all the time;
this change allows you to unit test routes and
their actions even when this.router is absent.

/cc @rwjblue
Merge pull request #9820 from machty/route-unit-test-send

[BUGFIX beta] Route.send is unit testable