Remove guard in `treeForAddon` around `addon/**/*.js` files.
Remove guard in `treeForAddon` around `addon/**/*.js` files.

This guard was added to avoid wasted effort when preprocessing
the `addon/` directory when it only contains a single `.gitkeep`
file (or is non-existent). The assumption I made was that if
there are no `*.js` files inside the `addon/` directory, then
we didn't need to attempt to transpile it.

Unfortunately, "back in reality" there are a number of addons
that wrap existing libraries, that have no `addon/**/*.js` files
but still need the `this._super.treeForAddon` invocation to process
the provided tree.

This change, reverts the guard (it was only a relatively small savings
anyways).

asakusuma/ember-cli,seawatts/ember-cli,HeroicEric/ember-cli,thoov/ember-cli,mike-north/ember-cli,cibernox/ember-cli,balinterdi/ember-cli,HeroicEric/ember-cli,kellyselden/ember-cli,kanongil/ember-cli,trentmwillis/ember-cli,sivakumar-kailasam/ember-cli,cibernox/ember-cli,akatov/ember-cli,asakusuma/ember-cli,patocallaghan/ember-cli,romulomachado/ember-cli,ef4/ember-cli,patocallaghan/ember-cli,gfvcastro/ember-cli,ef4/ember-cli,fpauser/ember-cli,jgwhite/ember-cli,ember-cli/ember-cli,mike-north/ember-cli,twokul/ember-cli,ember-cli/ember-cli,kanongil/ember-cli,seawatts/ember-cli,Turbo87/ember-cli,twokul/ember-cli,akatov/ember-cli,elwayman02/ember-cli,jgwhite/ember-cli,kellyselden/ember-cli,jgwhite/ember-cli,fpauser/ember-cli,seawatts/ember-cli,mike-north/ember-cli,jgwhite/ember-cli,cibernox/ember-cli,pzuraq/ember-cli,gfvcastro/ember-cli,fpauser/ember-cli,twokul/ember-cli,calderas/ember-cli,Turbo87/ember-cli,thoov/ember-cli,kategengler/ember-cli,kellyselden/ember-cli,ef4/ember-cli,romulomachado/ember-cli,twokul/ember-cli,rtablada/ember-cli,sivakumar-kailasam/ember-cli,sivakumar-kailasam/ember-cli,HeroicEric/ember-cli,kanongil/ember-cli,raycohen/ember-cli,patocallaghan/ember-cli,calderas/ember-cli,elwayman02/ember-cli,jrjohnson/ember-cli,Turbo87/ember-cli,kellyselden/ember-cli,ember-cli/ember-cli,jrjohnson/ember-cli,ef4/ember-cli,gfvcastro/ember-cli,rtablada/ember-cli,akatov/ember-cli,sivakumar-kailasam/ember-cli,calderas/ember-cli,calderas/ember-cli,romulomachado/ember-cli,pzuraq/ember-cli,thoov/ember-cli,thoov/ember-cli,seawatts/ember-cli,fpauser/ember-cli,kategengler/ember-cli,buschtoens/ember-cli,mike-north/ember-cli,trentmwillis/ember-cli,pzuraq/ember-cli,rtablada/ember-cli,kanongil/ember-cli,pzuraq/ember-cli,cibernox/ember-cli,Turbo87/ember-cli,trentmwillis/ember-cli,trentmwillis/ember-cli,romulomachado/ember-cli,rtablada/ember-cli,raycohen/ember-cli,akatov/ember-cli,buschtoens/ember-cli,balinterdi/ember-cli,HeroicEric/ember-cli,gfvcastro/ember-cli,patocallaghan/ember-cli