Drop signing_dir option from configure_auth_token_middleware

This is no longer being used due to Keystone PKI tokens no longer
being implemented.

In order to not break backward compatibility we create a new function
that is to be used instead and deprecate the old one. Modify the old
function to ignore the 3rd argument and display a deprecation warning.
Adjust callers to no longer create and set that directory, calling the
new function instead.

Change-Id: Id0dec1ba72467cce5cacfcfdb2bc0af2bd3a3610
8 files changed