bump pycadf to 0.6.0

v0.6.0 introduces support for a federated credential model, which is
required for keystone to emit audit notifications during federated
authentication in bp audit-support-for-federation

Change-Id: I6c07adf3c06398441a8c38be656c682687a9eb2f
Merge "bump pycadf to 0.6.0"