...avoiding the confusing, and apparently unnecessary back-and-forth between
system path and file URL.  (Superseding
<https://gerrit.libreoffice.org/#/c/50422/> "Don't overwrite system temppath
with old one that failed already".)

Change-Id: I247982a40d54565f5c98bda9a36209cba83c5c9f
Reviewed-on: https://gerrit.libreoffice.org/50494Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>