When OPTIONS methods (or verb) is disabled (or denied) on a IIS 10.0
web server, error 404 (e.g. 'Not Found') is emitted, so we need to deal
with it.

Change-Id: Ifd6df0ea4b89824133e212f73950d6c3acd00dd7
Reviewed-on: https://gerrit.libreoffice.org/28430Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Giuseppe Castagno <giuseppe.castagno@acca-esse.eu>