[2.1] same boot image listed multiple times

[Mihai Gheorghe]

The same image is being listed multiple times under deploy tab in maas ui.
The problem appears when using multiple rack controllers. When a rack controller syncs the images from the region controller, it returns the image name after sync to the region controller that lists it under the deployment tab. So for every rack controller there will be the same image entry under deployment tab.

e.g. In a deployment with 3 rack controllers, the xenial image will be listed three times under deployment tab, even though it's the same image. Selecting any of the entryes will work.

The duplicates should be filtered out and only one entry should be kept in the UI.