EMF+: Line thickness has to be considered when drawing the caps.

Change-Id: I6043ee3c214f453afaef06125993c73be624c07e
Reviewed-on: https://gerrit.libreoffice.org/6832
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>