sc: refactor ScDrawTextObjectBar::ExecuteAttr

Avoid code duplication, and make some actions to not depend
on args.

Change-Id: Ie2b32864f567f636843fb552bb0763e527322551
Reviewed-on: https://gerrit.libreoffice.org/7991
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>