Make removing nodes from scaled items possible.

This makes it possible to remove a dead node (e.g. if NovaCompute2 has
failed, regenerate the template with ,2 in the scale parameter, and
NovaCompute2 will not be enumerated.

Change-Id: I65d85a88152ed4adee60895173f8a05611a6440b
Merge "Make removing nodes from scaled items possible."