Origin's openstack.go does not support ca-file cloud provider attribute

[dougsaus]

The Kubernetes openstack.go supports ca-file cloud provider attribute but origin's openstack.go does not: see kubernetes code here

My openstack provider does not allow api-key auth so need ability to pass a ca-file to the cloud provider for v3 ssl authentication.

[mfojtik]

@Delmonte3161 we should get that attribute after 1.6 rebase lands as this flag was added a month ago (kubernetes/kubernetes@e3c8a0c).