Honor the padding value even if the border is not visible.
Previously the padding information was just thrown out, and
the image scaled to fill the entire image size.

The unit test for tdf#77454 needed to be tweaked because surprisingly
it has border padding of 1 - which this patch turns into a negative crop.

Change-Id: I866d26e00f27221239d3291404f70fb57ac0896d
Reviewed-on: https://gerrit.libreoffice.org/30578Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Justin Luth <justin_luth@sil.org>