966d20e3 "CMIS ucp: write documents back to CMIS
server" had introduced changes to sfx2/source/doc/docfile.cxx in LO 3.6 that
changed the exact commands that this code issued for UCP content nodes.  The GIO
UCP was not prepared to handle that, causing saving of documents via it to fail
with rather obscure error messages:

* For one, docfile.cxx started to call "getPropertyValues" to obtain the "Title"
  of a non-existent content.  That lead to an InteractiveAugmentedIOException
  instead of silently returning a void value.

* For another, docfile.cxx started to call "transfer" on a folder content whose
  URL did not have a trailing slash, so the code computed a wrong URL for the
  child element, resulting in various problems depending on context.

Change-Id: I1a9c0c094f5320456940e3af4c802711828ab5ac