It is not possible to create a target

Hello, i can not create a target, the python fouls and gwcli crashes out

```
[root@ceph1 ~]# gwcli
/iscsi-target> create iqn.1998-01.com.mycompany:myserver
IOError: [Errno 22] Invalid argument
```

```
[root@ceph1 ~]# gwcli
/iscsi-target> /iscsi-target create iqn.2003-01.com.redhat.iscsi-gw:hosting
IOError: [Errno 22] Invalid argument
```

Traceback:
```
/> /iscsi-target create iqn.2003-01.com.redhat.iscsi-gw:hosting
CMD: /iscsi create iqn.2003-01.com.redhat.iscsi-gw:hosting
Traceback (most recent call last):
File "/usr/bin/gwcli", line 187, in
main()
File "/usr/bin/gwcli", line 119, in main
shell.run_interactive()
File "/usr/lib/python2.7/site-packages/configshell_fb/shell.py", line 905, in run_interactive
self._cli_loop()
File "/usr/lib/python2.7/site-packages/configshell_fb/shell.py", line 734, in _cli_loop
self.run_cmdline(cmdline)
File "/usr/lib/python2.7/site-packages/configshell_fb/shell.py", line 848, in run_cmdline
self._execute_command(path, command, pparams, kparams)
File "/usr/lib/python2.7/site-packages/configshell_fb/shell.py", line 823, in _execute_command
result = target.execute_command(command, pparams, kparams)
File "/usr/lib/python2.7/site-packages/configshell_fb/node.py", line 1406, in execute_command
return method(*pparams, **kparams)
File "/usr/lib/python2.7/site-packages/gwcli/gateway.py", line 222, in ui_command_create
local_lio = root.RTSRoot()
File "/usr/lib/python2.7/site-packages/rtslib_fb/root.py", line 85, in __init__
self._set_dbroot_if_needed()
File "/usr/lib/python2.7/site-packages/rtslib_fb/root.py", line 167, in _set_dbroot_if_needed
fwrite(dbroot_path, self._preferred_dbroot+"\n")
File "/usr/lib/python2.7/site-packages/rtslib_fb/utils.py", line 79, in fwrite
file_fd.write(str(string))
IOError: [Errno 22] Invalid argument

```

Packet version:
targetcli-2.1.fb47-0.1.20170815.git5bf3517.el7.noarch
python-rtslib-2.1.fb64-2.el7.noarch
tcmu-runner-v1.3.0-0.4.23.g68fee8c.x86_64
ceph-iscsi-config-2.3-33.gae18773.el7.noarch
ceph-iscsi-cli-2.5-75.g8181a92.el7.noarch

kernel: Linux ceph1 4.14.13-1.el7.elrepo.x86_64

In this case, the target is created with the kernel-3.10.0-693.11.6.el7.x86_64, but the kernel does not pass the version check and the disks can not be added

If you add a target on the old kernel and boot into the new one, then rbd-target-gw and rbd-target-cli crush