Drive by cleanup.
Don't re-render panel when hiding notification.

All we need is to clear the notification, so stick to that.
Usability tweak to improve notifications.
Merge pull request #313 from kadams54/fix-deployer-notifications

### QA

To test:

1. Drag and drop the first charm.
2. Click the Deploy button and verify the summary is correct, but don't confirm. Cancel or close the summary.
3. Drag and drop the second charm.
4. Click the Deploy button - used to be you'd get a "no uncommitted changes" message. Now you'll now see the expected list of two services and two units.