Fix traceback unlocking encrypted pool

TrueNAS-11.3-MASTER-201912160916

Locked a pool in new UI, switched to Legacy, received traceback when attempting to unlock pool. Debug attached.

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Environment:

Software Version: TrueNAS-11.3-MASTER-201912160916 (6debe262d)
Request Method: GET
Request URL: http://tn09.lab.ixsystems.com/legacy/storage/volume/7/unlock/

Traceback:
File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py" in inner
42. response = get_response(request)
File "/usr/local/lib/python3.7/site-packages/django/core/handlers/base.py" in _legacy_get_response
249. response = self._get_response(request)
File "/usr/local/lib/python3.7/site-packages/django/core/handlers/base.py" in _get_response
178. response = middleware_method(request, callback, callback_args, callback_kwargs)
File "./freenasUI/freeadmin/middleware.py" in process_view
163. return login_required(view_func)(request, *view_args, **view_kwargs)
File "/usr/local/lib/python3.7/site-packages/django/contrib/auth/decorators.py" in _wrapped_view
23. return view_func(request, *args, **kwargs)
File "./freenasUI/storage/views.py" in volume_unlock
1008. form = forms.UnlockPassphraseForm()
File "./freenasUI/storage/forms.py" in _init_
2805. c.call('pool.unlock_services_restart_choices').items()
File "./freenasUI/storage/forms.py" in _init_
2805. c.call('pool.unlock_services_restart_choices').items()
File "/usr/local/lib/python3.7/site-packages/middlewared/client/client.py" in call
507. raise ClientException(c.error, c.errno, c.trace, c.extra)

Exception Type: ClientException at /legacy/storage/volume/7/unlock/
Exception Value: [id] attribute required