While all other clients should use internalURL, the Magnum client itself
and Keystone interface for trustee credentials should be publicly
accessible (upstream default when no config is specified) since
instances need to be able to reach them.

Closes-Bug: #1885420
Change-Id: I74359cec7147a80db24eb4aa4156c35d31a026bf

Magnum, Cinder and Octavia clients in Magnum now use endpoint_type of
internalURL by default consistent with other clients also used by the
conductor. Additionally, they also use the globally defined
`openstack_region_name` for region_name.

Closes-Bug: #1885096

Change-Id: Ibec511013760cc4f681a2ec1b769b532be3daf2d