Fix inspector breakage post-service double click.

Full confession: I didn't actually do anything to fix the inspector breakage. I was able to duplicate the bug a few times initially and then unable to duplicate once I started working on it. The destructor in `viewlet-manager.js` should handle removing the DOM node, which is what I thought the original problem was.

Instead I ended up removing the double click event, since there's no longer any difference between clicking once and clicking twice.

## QA

With the `il` flag.

1. Drag a charm to the canvas
2. Deploy it
3. Double click on the service icon
4. Close the inspector

Ensure the sidebar does not break and reverts back to the charmbrowser as expected. You can also inspect the DOM and make sure `<div class="bws-content">` has only one child.