...and the hack to locally introduce a bogus pupblished forward declaration of
XFormOperations with which this has been worked around in
cf5c3691 "INTEGRATION: CWS dba23b: work around
idlc limitation, which does not allow to refer unpublished interfaces as
optional entities in published services" no longer works in
offapi/type_reference/offapi.idl.

So given FormController is a (deprecated, even) old-style service (i.e., little
more than glorified commentary), the best fix probably is to demote the
problematic optional property to a comment.

Change-Id: Ia38483c817dc1762ba73315abcd4f9f063db3093