Break down groups into subsystems

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)

cgroups/fs/cpuset.go

@@ -0,0 +1,28 @@
+package fs
+
+import (
+	"os"
+)
+
+type cpusetGroup struct {
+}
+
+func (s *cpusetGroup) Set(d *data) error {
+	// we don't want to join this cgroup unless it is specified
+	if d.c.CpusetCpus != "" {
+		dir, err := d.join("cpuset")
+		if err != nil && d.c.CpusetCpus != "" {
+			return err
+		}
+		defer func() {
+			if err != nil {
+				os.RemoveAll(dir)
+			}
+		}()
+
+		if err := writeFile(dir, "cpuset.cpus", d.c.CpusetCpus); err != nil {
+			return err
+		}
+	}
+	return nil
+}