fix systemd cgroup path error in integration test

[lifubang]

When I run integration test with systemd cgroup driver in a container, I got some errors like this:

root@f7c63618dde3:/opt/mygo/src/github.com/opencontainers/runc# RUNC_USE_SYSTEMD=1 bats tests/integration/delete.bats 
 ✓ runc delete
 ✓ runc delete --force
 ✓ runc delete --force ignore not exist
 ✗ runc delete --force in cgroupv1 with subcgroups
   (from function `fail' in file tests/integration/helpers.bash, line 266,
    in test file tests/integration/delete.bats, line 91)
     `[ -d "${path}" ] || fail "test failed to create memory sub-cgroup ($path not found)"' failed
   runc spec (status=0):
   
   runc run -d --console-socket /tmp/bats-run-211890/runc.3qcU9w/tty/sock test_busybox (status=0):
   
   runc state test_busybox (status=0):
   {
     "ociVersion": "1.0.2-dev",
     "id": "test_busybox",
     "pid": 212304,
     "status": "running",
     "bundle": "/tmp/bats-run-211890/runc.3qcU9w/bundle",
     "rootfs": "/tmp/bats-run-211890/runc.3qcU9w/bundle/rootfs",
     "created": "2021-03-10T04:12:48.316070083Z",
     "owner": ""
   }
   runc exec test_busybox sh (status=0):
   + cd /sys/fs/cgroup/memory
   + mkdir foo
   + cd foo
   + echo 7
   + cat tasks
   7
   + cd /sys/fs/cgroup/freezer
   + mkdir foo
   + cd foo
   + echo 7
   + cat tasks
   7
   test failed to create memory sub-cgroup (/sys/fs/cgroup/memory/machine.slice/runc-cgroups-integration-test-1001.scope/foo not found)
 - runc delete --force in cgroupv2 with subcgroups (skipped: test requires cgroups_v2)

5 tests, 1 failure, 1 skipped

The cgroup mount info looks like:

root@f7c63618dde3:/opt/mygo/src/github.com/opencontainers/runc# cat /proc/self/mountinfo | grep cgroup
433 432 0:117 / /sys/fs/cgroup ro,nosuid,nodev,noexec shared:134 - tmpfs tmpfs ro,mode=755
434 433 0:30 /docker/f7c63618dde3a5af6632fe0e7cc2d4e6be70be0b3f273d90b9f615e60f901c1e /sys/fs/cgroup/cpuset rw,nosuid,nodev,noexec,relatime shared:135 master:19 - cgroup cpuset rw,cpuset
481 433 0:31 /docker/f7c63618dde3a5af6632fe0e7cc2d4e6be70be0b3f273d90b9f615e60f901c1e /sys/fs/cgroup/cpu rw,nosuid,nodev,noexec,relatime shared:136 master:20 - cgroup cpu rw,cpu
482 433 0:32 /docker/f7c63618dde3a5af6632fe0e7cc2d4e6be70be0b3f273d90b9f615e60f901c1e /sys/fs/cgroup/cpuacct rw,nosuid,nodev,noexec,relatime shared:137 master:21 - cgroup cpuacct rw,cpuacct
483 433 0:33 /docker/f7c63618dde3a5af6632fe0e7cc2d4e6be70be0b3f273d90b9f615e60f901c1e /sys/fs/cgroup/blkio rw,nosuid,nodev,noexec,relatime shared:138 master:22 - cgrou blkio rw,blkio
484 433 0:34 /docker/f7c63618dde3a5af6632fe0e7cc2d4e6be70be0b3f273d90b9f615e60f901c1e /sys/fs/cgroup/memory rw,nosuid,nodev,noexec,relatime shared:139 master:23 - cgroup memory rw,memory
485 433 0:35 /docker/f7c63618dde3a5af6632fe0e7cc2d4e6be70be0b3f273d90b9f615e60f901c1e /sys/fs/cgroup/devices rw,nosuid,nodev,noexec,relatime shared:140 master:24 - cgroup devices rw,devices
486 433 0:36 /docker/f7c63618dde3a5af6632fe0e7cc2d4e6be70be0b3f273d90b9f615e60f901c1e /sys/fs/cgroup/freezer rw,nosuid,nodev,noexec,relatime shared:141 master:25 - cgroup freezer rw,freezer
487 433 0:37 /docker/f7c63618dde3a5af6632fe0e7cc2d4e6be70be0b3f273d90b9f615e60f901c1e /sys/fs/cgroup/net_cls rw,nosuid,nodev,noexec,relatime shared:142 master:26 - cgroup net_cls rw,net_cls
488 433 0:38 /docker/f7c63618dde3a5af6632fe0e7cc2d4e6be70be0b3f273d90b9f615e60f901c1e /sys/fs/cgroup/perf_event rw,nosuid,nodev,noexec,relatime shared:143 master:27 - cgroup perf_event rw,perf_event
489 433 0:39 /docker/f7c63618dde3a5af6632fe0e7cc2d4e6be70be0b3f273d90b9f615e60f901c1e /sys/fs/cgroup/net_prio rw,nosuid,nodev,noexec,relatime shared:144 master:28 - cgroup net_prio rw,net_prio
490 433 0:40 /docker/f7c63618dde3a5af6632fe0e7cc2d4e6be70be0b3f273d90b9f615e60f901c1e /sys/fs/cgroup/hugetlb rw,nosuid,nodev,noexec,relatime shared:145 master:29 - cgroup hugetlb rw,hugetlb
491 433 0:41 /docker/f7c63618dde3a5af6632fe0e7cc2d4e6be70be0b3f273d90b9f615e60f901c1e /sys/fs/cgroup/pids rw,nosuid,nodev,noexec,relatime shared:146 master:30 - cgroup pids rw,pids
492 433 0:42 / /sys/fs/cgroup/rdma rw,nosuid,nodev,noexec,relatime shared:147 master:31 - cgroup rdma rw,rdma
493 433 0:43 /docker/f7c63618dde3a5af6632fe0e7cc2d4e6be70be0b3f273d90b9f615e60f901c1e /sys/fs/cgroup/systemd rw,nosuid,nodev,noexec,relatime shared:148 master:32 - cgroup cgroup rw,name=systemd
293 433 0:121 / /sys/fs/cgroup/unified rw,nosuid,nodev,noexec,relatime shared:149 - cgroup2 cgroup2 rw,nsdelegate

Signed-off-by: lifubang lifubang@acmcoder.com

[kolyshkin]

Please provide steps to repro (I was not able to).

1. Is the container you run things in using cgroupns?
2. If this is a rootless container, the fix might be in Fix cgroup2 mount for rootless case #2818

[kolyshkin]

@lifubang #2845 (comment) 🙏🏻

[lifubang]

@lifubang #2845 (comment) 🙏🏻

1. Run a container in a mac :
   docker run -dit —privileged -v /var/lib/docker —entrypoint=/sbin/init Ubuntu:20.04
2. Run the integration test inside this container.