Fix keystone_default_role for Horizon

Set correct value for Juno, upstream is up to date already:
https://github.com/stackforge/puppet-horizon/blob/master/manifests/init.pp#L180

Closes-bug: #1397265
Change-Id: Ida6833b29cc35ddd8fcc50a45ad4407b4e24170a
Merge "Fix keystone_default_role for Horizon"