gss relies on service_host (public api) endpoints ignoring ingress-address for the identity endpoint

ingress address provided by keystone is 10.232.6.200 (oam-space) while service_host is 10.232.45.236 (public space)

The LXD container used by GSS will only have an oam interface causing a silent connection failure as gss doesn't report anything via its status:

juju deploy cs:bionic/glance-simplestreams-sync --to lxd:4 --bind oam-space

  File "./glance-simplestreams-sync.py", line 495, in <module>
    main()
  File "./glance-simplestreams-sync.py", line 433, in main
    ksc = get_keystone_client(id_conf['api_version'])
  File "./glance-simplestreams-sync.py", line 188, in get_keystone_client
    project_id=os.environ['OS_PROJECT_ID'])
  File "/usr/lib/python2.7/dist-packages/keystoneclient/v3/client.py", line 250, in __init__
    self.authenticate()
  File "/usr/lib/python2.7/dist-packages/keystoneclient/httpclient.py", line 578, in authenticate
    resp = self.get_raw_token_from_identity_service(**kwargs)
  File "/usr/lib/python2.7/dist-packages/keystoneclient/v3/client.py", line 336, in get_raw_token_from_identity_service
    _('Authorization failed: %s') % e)
keystoneauth1.exceptions.auth.AuthorizationFailure: Authorization failed: Unable to establish connection to http://10.232.45.236:5000/v3/auth/tokens

juju run --unit glance-simplestreams-sync/1 'relation-get -r identity-service:65 - keystone/0'
admin_domain_id: 24eecdf281e544ba9d41bae91299ea5a
admin_token: Cg36p9Z2VVY8kXxpw4fqMj2mr9knGhjfBRW7gdXWGtF27Y86P6dhJYzX3RB9ffhy
api_version: "3"
auth_host: 10.232.6.200
auth_port: "35357"
auth_protocol: http
egress-subnets: 10.232.6.200/32
ingress-address: 10.232.6.200
private-address: 10.232.6.200
service_domain: service_domain
service_domain_id: 2510a9c3f8984216837e55dc3e25a344
service_host: 10.232.45.236
service_password: sKXt8VJkTwG8sxLtxLNnVjLYV4CNqW6Hcz7KdbHLTFLyyNjGH7dVJHz34fqsPbys
service_port: "5000"
service_protocol: http
service_tenant: services
service_tenant_id: 451a055f18b84f1c9b9b48e13bce754b
service_username: image-stream