libc/cg: convert r.CPU.Cpus/Mems to systemd props

Support for systemd properties AllowedCPUs and AllowedMemoryNodes
was added by commit 13afa58d0e, but only for unified resources
of systemd v2 driver.

This adds support for Cpu.Cpus and Cpu.Mems resources to
both systemd v1 and v2 cgroup drivers.

An integration test is added to check that the settings work.

[v2: check for systemd version]
[v3: same in the test]

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/cgroups/systemd/v1.go

@@ -90,6 +90,11 @@ func genV1ResourcesProperties(c *configs.Cgroup, conn *systemdDbus.Conn) ([]syst
 			newProp("TasksMax", uint64(r.PidsLimit)))
 	}
 
+	err = addCpuset(conn, &properties, r.CpusetCpus, r.CpusetMems)
+	if err != nil {
+		return nil, err
+	}
+
 	return properties, nil
 }