Move authtoken configuration out of paste.ini
    
    Makes use of https://review.openstack.org/#/c/10579/
    to avoid site-specific data in paste.ini files.
    
    To complete Glance with Keystone configuration:
    openstack-config --set /etc/glance/glance-api.conf paste_deploy flavor keystone
    
    openstack-config --set /etc/glance/glance-api.conf keystone_authtoken admin_tenant_name SERVICE_TENANT_NAME
    openstack-config --set /etc/glance/glance-api.conf keystone_authtoken admin_user SERVICE_USER
    openstack-config --set /etc/glance/glance-api.conf keystone_authtoken admin_password SERVICE_PASSWORD
    
    and repeat the same in glance-registry.conf !