magnum names kubernetes clusters contexts with invalid character

[Clenimar Filemon]

when one creates a kubernetes clusters using magnum, the cluster context name follows the pattern "default/<cluster_name>":

$ kubectl config get-contexts
CURRENT NAME CLUSTER AUTHINFO
NAMESPACE
* default/clenimar-kube-c1 clenimar-kube-c1 clenimar-kube-c1

we should not use slashes in contexts names, as some tools may complain about it.
e.g.
$ kubefed join --context=fed clenimar-kube-c1 --host-cluster-context=default/clenimar-kube-c1 --cluster-context=default/clenimar-kube-c1
error: invalid resource name "cluster-default/clenimar-kube-c1": [may not contain '/']

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/python-magnumclient 2.7.0 release.