...and use it so that private: URLs are not needlessly passed to the gio or
gnome-vfs "catch-all" UCPs.
Change-Id: I85d100567d1641130449fe21ccd072bcc0ec0979
see https://gerrit.libreoffice.org/#/c/3367/
and Change-Id: I00c96fa77d04b33a6f8c8cd3490dfcd9bdc9e84a for details
Change-Id: I199a75bc4042af20817265d5ef85b1134a96ff5a