to disable the possibility to update installed extensions

Change-Id: Ifdee0f3b13ee3e2bcb288c8ded98cb9805a6e55a
Reviewed-on: https://gerrit.libreoffice.org/16059Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>