Fix locking of public UriReference members again

Fix locking of public UriReference members again

...after 074790ad6f4e02e7aed3f9c954f0b4005b40fa21 "remove some locking from
UriReference" (and its follow-up 0f44815ce7b2925189cd603853ce55d8363549dd
"loplugin:constmethods"):  The m_path member is modified by
UrlReference::setName in
stoc/source/uriproc/UriSchemeParser_vndDOTsunDOTstarDOTscript.cxx.  Also make
the non-mutated members (for which locking is thus indeed not needed) private
for now.  (The original intention was that there can be further parsers for
other URI schemes, which might need to modify further UriReference members.  If
such further parsers are ever implemented, the relevant members can be made
public again, and the locking be restored where necessary.)

Change-Id: I80b437fe14f43294a52e465a7e1f31ddf2ab0482
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/120749
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>