Comment 5 for bug 1988366

Ceph-iSCSI is a bit complicated example as a reproducer
https://docs.ceph.com/en/quincy/rbd/iscsi-overview/
But the simplest reproducer is `targetctl clear` with jammy HWE kernel.

$ sudo targetctl clear
Traceback (most recent call last):
  File "/usr/bin/targetctl", line 82, in <module>
    main()
  File "/usr/bin/targetctl", line 79, in main
    funcs[sys.argv[1]](savefile)
  File "/usr/bin/targetctl", line 57, in clear
    RTSRoot().clear_existing(confirm=True)
  File "/usr/lib/python3/dist-packages/rtslib_fb/root.py", line 318, in clear_existing
    so.delete()
  File "/usr/lib/python3/dist-packages/rtslib_fb/tcm.py", line 269, in delete
    for lun in self._gen_attached_luns():
  File "/usr/lib/python3/dist-packages/rtslib_fb/tcm.py", line 215, in _gen_attached_luns
    for tpgt_dir in listdir(tpgts_base):
NotADirectoryError: [Errno 20] Not a directory: '/sys/kernel/config/target/iscsi/cpus_allowed_list'