This change add a container manager inside the dockershim to move docker daemon
and associated processes to a specified cgroup. The original kubelet container
manager will continue checking the name of the cgroup, so that kubelet know how
to report runtime stats.
`--kubelet-cgroups` and `--system-cgroups` respectively.
Updated `--runtime-container` to `--runtime-cgroups`.
Cleaned up most of the kubelet code that consumes these flags to match
the flag name changes.
Signed-off-by: Vishnu kannan <vishnuk@google.com>