NAS-110773 / 21.08 / Fix kerberos error (by themylogin)

[bugclerk]

https://jira.ixsystems.com/browse/NAS-110214

Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/middlewared/job.py", line 367, in run
    await self.future
  File "/usr/local/lib/python3.8/site-packages/middlewared/job.py", line 403, in __run_body
    rv = await self.method(*([self] + args))
  File "/usr/local/lib/python3.8/site-packages/middlewared/plugins/smb.py", line 473, in configure
    await self.middleware.call("directoryservices.initialize")
  File "/usr/local/lib/python3.8/site-packages/middlewared/main.py", line 1238, in call
    return await self._call(
  File "/usr/local/lib/python3.8/site-packages/middlewared/main.py", line 1195, in _call
    return await methodobj(*prepared_call.args)
  File "/usr/local/lib/python3.8/site-packages/middlewared/plugins/directoryservices.py", line 416, in initialize
    await self.middleware.call('kerberos.start')
  File "/usr/local/lib/python3.8/site-packages/middlewared/main.py", line 1238, in call
    return await self._call(
  File "/usr/local/lib/python3.8/site-packages/middlewared/main.py", line 1195, in _call
    return await methodobj(*prepared_call.args)
  File "/usr/local/lib/python3.8/site-packages/middlewared/plugins/kerberos.py", line 577, in start
    await asyncio.wait_for(self._kinit(), timeout=kinit_timeout)
  File "/usr/local/lib/python3.8/asyncio/tasks.py", line 494, in wait_for
    return fut.result()
  File "/usr/local/lib/python3.8/site-packages/middlewared/plugins/kerberos.py", line 322, in _kinit
    await self.do_kinit(ldap)
  File "/usr/local/lib/python3.8/site-packages/middlewared/plugins/kerberos.py", line 273, in do_kinit
    elif dstype == DSType.LDAP:
  File "/usr/local/lib/python3.8/enum.py", line 384, in __getattr__
    raise AttributeError(name) from None
AttributeError: LDAP

Original PR: #6863
Jira URL: https://jira.ixsystems.com/browse/NAS-110773

[bugclerk]

Jira URL: https://jira.ixsystems.com/browse/NAS-110773