feat(app-emulation/docker): bump docker-0.8.1-r1

In the last patch I modified docker-0.8.1.ebuild directly. That was
wrong. This time I copy the ebuild, add the epatch and leave
docker-0.8.0 unmodified. This also changes the patch to reflect what is
waiting for a merge upstream.
Merge pull request #377 from philips/docker-0.8.1-fix-sa2

feat(app-emulation/docker): bump docker-0.8.1-r1