5xx on slaves cvs export in racks

[Igor Shishkin]

Hello,

Internal Server Error: /export/jenkins_ci/slaves.csv
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/django/core/handlers/base.py", line 112, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python2.7/dist-packages/django/contrib/auth/decorators.py", line 22, in _wrapped_view
    return view_func(request, *args, **kwargs)
  File "./jenkins_ci/views/misc.py", line 22, in export_jenkins_slaves
    row = [n.instance.name, n.name, n.formatted_address, n.all_labels, n.last_job, n.executors,
AttributeError: 'NoneType' object has no attribute 'name'

[Alexander Charykov (acharykov)]

Fixed in https://review.fuel-infra.org/#/c/22505