EUCA-7770 - Ensure that "deferred" tag creation adds the new tags to the model collection so they can be parsed later.

https://eucalyptus.atlassian.net/browse/EUCA-7770

If the "defer" is used to prevent the tag editor from saving the tags directly because we want to do it manually later, go ahead and add the new tags to the model's tag collection. They're expected to be there for those operations.