memcg_control from ubuntu_ltp_controllers failed (Failed to open memory.memsw.limit_in_bytes for writing: Permission denied)

[Po-Hsu Lin]

This bug is split out from bug 1983659

memcg_control test is failing with:
    memcg_control_test 1 TINFO: Test #1: Checking if the memory usage limit imposed by the topmost group is enforced
    tst_rod: Failed to open '/sys/fs/cgroup/memory/ltp/test-18872/memory.memsw.limit_in_bytes' for writing: Permission denied
    memcg_control_test 1 TBROK: echo 4096 > /sys/fs/cgroup/memory/ltp/test-18872/memory.memsw.limit_in_bytes failed

Test log:
INFO: Test start time: Tue Jun 13 15:49:22 UTC 2023
COMMAND: /opt/ltp/bin/ltp-pan -q -e -S -a 18831 -n 18831 -f /tmp/ltp-HdDSIAqMJj/alltests -l /dev/null -C /dev/null -T /dev/null
LOG File: /dev/null
FAILED COMMAND File: /dev/null
TCONF COMMAND File: /dev/null
Running tests.......
memcg_control_test 1 TINFO: timeout per run is 0h 5m 0s
memcg_control_test 1 TINFO: Test starts with cgroup version 1
memcg_control_test 1 TINFO: Test #1: Checking if the memory usage limit imposed by the topmost group is enforced
tst_rod: Failed to open '/sys/fs/cgroup/memory/ltp/test-18872/memory.memsw.limit_in_bytes' for writing: Permission denied
memcg_control_test 1 TBROK: echo 4096 > /sys/fs/cgroup/memory/ltp/test-18872/memory.memsw.limit_in_bytes failed
memcg_control_test 1 TINFO: AppArmor enabled, this may affect test results
memcg_control_test 1 TINFO: it can be disabled with TST_DISABLE_APPARMOR=1 (requires super/root)
memcg_control_test 1 TINFO: loaded AppArmor profiles: none

Summary:
passed 0
failed 0
broken 1
skipped 0
warnings 0
INFO: ltp-pan reported some tests FAIL
LTP Version: 20220527
INFO: Test end time: Tue Jun 13 15:49:22 UTC 2023