OLE: Turn an OSL_ENSURE() into a real condition (related: fdo#65631)

This is part of some STAMPIT workaround; no idea what it is, but for sure it
causes problems with PowerPoint OLE in Writer - so let's avoid updating if it
is not "STAMPIT".

This appears to help for the problem in fdo#65631 comment #9 on master,
let's see if the same is true if it's backported to 4.2...

(cherry picked from commit a94e973bf5b5d0755a53881867961691633a4cbd)
Signed-off-by: Michael Stahl <mstahl@redhat.com>

Change-Id: I266b419ba3461c547f7ee8e447ef64a47a8511e8