Move static pProgress into properties container

Change-Id: I0e2843327173b9459b1b5bf73277b106c495ecef
Reviewed-on: https://gerrit.libreoffice.org/12486
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>