GUI-1079: Allow images to be de-registered from the cloud

Implements https://eucalyptus.atlassian.net/browse/GUI-1079
I don't disagree that "all()" is useful. Particularly where this is a list of items (since that what it was meant for). In this case, a list of 2 is constructed to make use of "all()" where a simple "and" would be simpler and clearer.