use ros_buildfarm old_release_set.Dockerfile.em

[mikaelarguedas]

Requires ros-infrastructure/ros_buildfarm#637

Now that this template will start being used on more recent distros as well as non Ubuntu distros. We should not apply the sed for old-releases unconditionnaly.

This PR switches to using the template used by the ros_buildfarm instead

@nuclearsandwich FYI

[mikaelarguedas]

Due to difficulties to reach packages.ros.org without too much latency, I haven't been able to generate all dockerfiles and see if the resulting Dockerfiles makes sense.
@nuclearsandwich could you try to generate them along #63 + #64 and push the resulting files to osrf/docker_images#273 if they look valid? Thanks!

[mikaelarguedas]

just read osrf/docker_images#273 (comment),
I also noticed that the old ros distro target some ubuntu versions not listed in the buildfarm template.

So let's defer this improvement to allow osrf/docker_images#273 to move forward

[mikaelarguedas]

now that ros-infrastructure/ros_buildfarm#637 has been merged, I believe this is ready for review/merge