context in docker utils missing

magnum/magnum/common/docker_utils.py (branch: master) line 62 needs to be changed:

from:
<magnum_cert) = cert_manager.create_client_files(cluster)
to:
>magnum_cert) = cert_manager.create_client_files(cluster, context)

otherwise the periodic lookups fail with:
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic Traceback (most recent call last):
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic File "/usr/lib/python2.7/dist-packages/magnum/service/periodic.py", line 157, in _send_cluster_metrics
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic monitor.pull_data()
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic File "/usr/lib/python2.7/dist-packages/magnum/drivers/swarm_fedora_atomic_v1/monitor.py", line 44, in pull_data
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic self.cluster) as docker:
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic File "/usr/lib/python2.7/contextlib.py", line 17, in __enter__
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic return self.gen.next()
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic File "/usr/lib/python2.7/dist-packages/magnum/common/docker_utils.py", line 62, in docker_for_cluster
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic magnum_cert) = cert_manager.create_client_files(cluster)
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic File "/usr/lib/python2.7/dist-packages/magnum/conductor/handlers/common/cert_manager.py", line 135, in create_client_files
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic ca_cert = get_cluster_ca_certificate(cluster, context)
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic File "/usr/lib/python2.7/dist-packages/magnum/conductor/handlers/common/cert_manager.py", line 118, in get_cluster_ca_certificate
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic context=context
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic File "/usr/lib/python2.7/dist-packages/magnum/common/cert_manager/x509keypair_cert_manager.py", line 80, in get_cert
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic x509keypair_obj = objects.X509KeyPair.get_by_uuid(context, cert_ref)
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic File "/usr/lib/python2.7/dist-packages/oslo_versionedobjects/base.py", line 184, in wrapper
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic result = fn(cls, context, *args, **kwargs)
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic File "/usr/lib/python2.7/dist-packages/magnum/objects/x509keypair.py", line 98, in get_by_uuid
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic db_x509keypair = cls.dbapi.get_x509keypair_by_uuid(context, uuid)
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic File "/usr/lib/python2.7/dist-packages/magnum/db/sqlalchemy/api.py", line 423, in get_x509keypair_by_uuid
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic query = self._add_tenant_filters(context, query)
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic File "/usr/lib/python2.7/dist-packages/magnum/db/sqlalchemy/api.py", line 122, in _add_tenant_filters
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic if context.is_admin and context.all_tenants:
2017-03-06 10:52:37.967 24661 ERROR magnum.service.periodic AttributeError: 'NoneType' object has no attribute 'is_admin'