This is a longstanding (at least since 2000: already present in commit
7b0b5cdf) error where left border linespace was used when calculating
right margin. It was copypasted from ww8 import to ooxml code verbatim.
The problem only manifests itself when left and right border spacings
are not the same; and since we had other errors in the borders import,
that additional problem simply wasn't apparent.

Also use scaled border width in border distance/margin calculations.

Unit tests updated.

Change-Id: I70961e1bde29471def69e1ef944ba2779cffe307
Reviewed-on: https://gerrit.libreoffice.org/51474Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>