Drop auth_token configs for api-paste.ini.

We now prefer to use cinder.conf to configure keystoneclients
auth_token configs.

Also, Devstack has now been update to allow this:

https://review.openstack.org/#/c/52259/

Related-Bug #1240753

Change-Id: I2a4b300af37eddf5010b97ca796f0552941642a8

etc/cinder/api-paste.ini

@@ -50,13 +50,3 @@ paste.filter_factory = cinder.api.middleware.auth:CinderKeystoneContext.factory
 
 [filter:authtoken]
 paste.filter_factory = keystoneclient.middleware.auth_token:filter_factory
-auth_host = 127.0.0.1
-auth_port = 35357
-auth_protocol = http
-admin_tenant_name = %SERVICE_TENANT_NAME%
-admin_user = %SERVICE_USER%
-admin_password = %SERVICE_PASSWORD%
-# signing_dir is configurable, but the default behavior of the authtoken
-# middleware should be sufficient.  It will create a temporary directory
-# in the home directory for the user the cinder process is running as.
-#signing_dir = /var/lib/cinder/keystone-signing