Enter cgroups while entering namespaces as part of NsEnter.
Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)
Enter cgroups as part of nsenter while using systemd.
Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)
Store all the cgroups paths as part of the state. This simplifies entering cgroups and will be useful for
cleanups too in the future.
Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)
Update cgroups paths in state to be a map with cgroup type as key and path as value.
Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)
Cleanup systemd cgroup code

The current paths for the different systemd cgroup subsystems that
systemd manages and that we have to manage are very inconsistent.  This
patch cleans up those differences and allows consistent paths to be
used.

Signed-off-by: Michael Crosby <michael@docker.com>
Merge pull request #4 from crosbymichael/cgroup-enter

Cleanup systemd cgroup code
Merge pull request #143 from vishh/enter_cgroup

Enter cgroups as part of NsEnter