Do not re-render MV if already exists.
Merge pull request #352 from kadams54/only-one-mv

### QA

1. Switch to machine view.
2. Use the inspector to view bundle details for a bundle and then click on the button in the details panel to deploy it.
3. You should only see one copy of each machine show up in the machines column. One machine 0, one machine 1. Not three of each.

Do some other playing around, switching between the canvas and MV (i.e., destroying MV, recreating it), etc. Make sure everything looks good.