Hack around exceptions thrown when closing the reference dialog

ce.ProtectedNode doesn't like to be torn down when it's detached,
and this was happening to CE nodes created in the MWReferenceList.

Hack around this by attaching the CE nodes generated by the
MWReferenceList to the ce.MWReferenceListNode (so they have a
parent and a way of getting to the surface), and by guarding against
multiple successive setups/teardowns in ce.ProtectedNode.

Change-Id: If00e75b939ccbdbaf681bbb6609fec54805bf9a0
Merge "Hack around exceptions thrown when closing the reference dialog"