GUI-1231: VPC support for scaling group wizard and detail page

https://eucalyptus.atlassian.net/browse/GUI-1231
https://eucalyptus.atlassian.net/browse/GUI-1232
Why convert the list to a comma-separated string here?  We seem to be doing the opposite in line 317, so it's probably more efficient (and bug-proof) to remove the join() here and the split() further down, right?  Also, the join/split operations are inconsistent, since the join adds a space after the comma and the split doesn't account for that space.