Fixes rendering of unplaced service unit icons.

* Updated method to use db.units, and to add icon data to the units.
* Updated the template and CSS.

QA
* In service view, deploy mysql to the canvas.
* In the web console, run `app.db.addUnits([{id: 'mysql/10'}, {id: 'mysql/11'}])`
* You should get a response of a list of the units in the console.
* Go to machine view.
* You should see two mysql units in the unplaced section.