cpuset_regression_test in ubuntu_ltp_controllers failed with X arm64 (TBROK: Unable to prepare existing cpuset cgroups)

[Po-Hsu Lin]

Issue found with X-4.4, arm64 only.
I think it is the first time we ran this ubuntu_ltp_controllers test on it.

Test log:
INFO: Test start time: Sat Jun 24 05:00:11 UTC 2023
COMMAND: /opt/ltp/bin/ltp-pan -q -e -S -a 30796 -n 30796 -f /tmp/ltp-yADU3BaR1d/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.......
cpuset_regression_test 1 TINFO: timeout per run is 0h 5m 0s
cpuset_regression_test 1 TINFO: test starts with cgroup version 1
sh: echo: I/O error
cpuset_regression_test 1 TBROK: Unable to prepare existing cpuset cgroups
sh: echo: I/O error
cpuset_regression_test 1 TINFO: AppArmor enabled, this may affect test results
cpuset_regression_test 1 TINFO: it can be disabled with TST_DISABLE_APPARMOR=1 (requires super/root)
cpuset_regression_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: Sat Jun 24 05:00:11 UTC 2023

For s390x it's failing with bug 1985879.