Move the process outside of the systemd cgroup

If you don't move the process out of the named cgroup for systemd then
systemd will try to delete all the cgroups that the process is currently
in.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

libcontainer/cgroups/fs/apply_raw.go

@@ -31,6 +31,7 @@ var (
 		&NetPrioGroup{},
 		&PerfEventGroup{},
 		&FreezerGroup{},
+		&NameGroup{GroupName: "name=systemd", Join: true},
 	}
 	CgroupProcesses  = "cgroup.procs"
 	HugePageSizes, _ = cgroups.GetHugePageSize()

libcontainer/cgroups/fs/name.go

@@ -9,13 +9,18 @@ import (
 
 type NameGroup struct {
 	GroupName string
+	Join      bool
 }
 
 func (s *NameGroup) Name() string {
 	return s.GroupName
 }
 
 func (s *NameGroup) Apply(d *cgroupData) error {
+	if s.Join {
+		// ignore errors if the named cgroup does not exist
+		d.join(s.GroupName)
+	}
 	return nil
 }
 
@@ -24,6 +29,9 @@ func (s *NameGroup) Set(path string, cgroup *configs.Cgroup) error {
 }
 
 func (s *NameGroup) Remove(d *cgroupData) error {
+	if s.Join {
+		removePath(d.path(s.GroupName))
+	}
 	return nil
 }