Access to targetcli utility is completely forbidden upon creation of invalid wwn

Issue

• Can not delete invalid WWN created in targetcli.
• targetcli does not allow to modify targetcli configuration after creation of invalid wwn
• Targetcli adds system host name in the automatically generated iSCSI wwn names. If the system hostname has _ or Blank space then it is treated as invalid iqn/wwn name.

/> iscsi/ create 
Created target iqn.2003-01.org.linux-iscsi.rhel_storage2.x8664:sn.ef7eb28bb6ee.
Created TPG 1.
Global pref auto_add_default_portal=true
Created default portal listening on all IPs (0.0.0.0), port 3260.

/>ls
o- / ............................................................................ [...]
[...]
  o- iscsi ...................................................................... [Targets: 2]
  | o- iqn.2003-01.org.linux-iscsi.rhel_storage2.x8664:sn.ef7eb28bb6ee .......... [INVALID WWN]  <<<< Invalid wwn/iqn with "_"
  | | o- tpg1 ................................................................... [no-gen-acls, no-auth]
[...]

• After this targetcli won't allow to modify any of the current configuration not even deletion of invalid wwn.

/> iscsi/ delete iqn.2003-01.org.linux-iscsi.rhel_storage2.x8664:sn.ef7eb28bb6ee 
WWN not valid as: iqn, naa, eui

• While exiting from the targetcli system throws below call traces.

/> exit
Global pref auto_save_on_exit=true
Last 10 configs saved in /etc/target/backup.
Traceback (most recent call last):
  File "/usr/bin/targetcli", line 121, in <module>
    main()
  File "/usr/bin/targetcli", line 117, in main
    root_node.ui_command_saveconfig()
  File "/usr/lib/python2.7/site-packages/targetcli/ui_root.py", line 90, in ui_command_saveconfig
    self.rtsroot.save_to_file(savefile)
  File "/usr/lib/python2.7/site-packages/rtslib_fb/root.py", line 270, in save_to_file
    f.write(json.dumps(self.dump(), sort_keys=True, indent=2))
  File "/usr/lib/python2.7/site-packages/rtslib_fb/root.py", line 161, in dump
    d['targets'] = [t.dump() for t in self.targets]
  File "/usr/lib/python2.7/site-packages/rtslib_fb/root.py", line 81, in _list_targets
    for target in fabric_module.targets:
  File "/usr/lib/python2.7/site-packages/rtslib_fb/fabric.py", line 173, in _list_targets
    yield Target(self, self.from_fabric_wwn(wwn), 'lookup')
  File "/usr/lib/python2.7/site-packages/rtslib_fb/target.py", line 75, in __init__
    self.wwn, self.wwn_type = fabric_module.to_normalized_wwn(wwn)
  File "/usr/lib/python2.7/site-packages/rtslib_fb/fabric.py", line 193, in to_normalized_wwn
    return normalize_wwn(self.wwn_types, wwn)
  File "/usr/lib/python2.7/site-packages/rtslib_fb/utils.py", line 397, in normalize_wwn
    raise RTSLibError("WWN not valid as: %s" % ", ".join(wwn_types))
rtslib_fb.utils.RTSLibError: WWN not valid as: iqn, naa, eui

• The further access to targetcli will be completely forbidden with below error.

# targetcli 
WWN not valid as: iqn, naa, eui