Remove deprecated fields in keystone auth middleware

This commit makes the following changes:

Use X_PROJECT_ID instead of X_TENANT_ID:
  In the latest keystone auth_token middleware it is recommended to
  use X_PROJECT_ID instead of X_TENANT_ID. X_PROJECT_ID is supported
  in auth_token middleware for both keystone v2 and v3 API.
  The corresponding change was done in keystoneclient before Grizzly
  release, so we don't need to take care of X_TENANT_ID now.

USE X_ROLES instead of X_ROLE:
  X_ROLES is now recommended.
  X_ROLE exists just for diablo backward compatibility.

Remove X_TENANT and X_USER:
  X_TENANT and X_USER are for diablo backward compatibility.
  We no longer need take care of them in Icehouse Neutron.

Change-Id: Ie714b1323ff8c44dbee66b54e683226cf675b104
Closes-Bug: #1242447
Merge "Remove deprecated fields in keystone auth middleware"