Move auth_token configurations to quantum.conf

keystone auth_token middleware now allows quantum to have auth_token
configuration in quantum.conf. auth_token middleware supports
auth_token configuration both in api-paste.ini and quantum.conf,
so we can apply this change at any timing.

Change-Id: Ie5dd63e6c6938d2c8118e0f6090ef057c21a772a
Merge "Move auth_token configurations to quantum.conf"