Update the "cgroup-lite" dep in our deb package from "Suggests" to "Recommends" and add "cgroupfs-mount" as another alternative

I tested to verify that if neither package is available (for example, on Debian Wheezy), apt still continues installing properly.

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #5450 from tianon/update-deb-cgroup-dep

Update the "cgroup-lite" dep in our deb package from "Suggests" to "Recommends" and add "cgroupfs-mount" as another alternative