Remove unused methods from AuthInfo

The lookup_user and _assert_user_is_enabled methods in
keystone.auth.controllers.AuthInfo aren't used or tested, so
remove them.

Change-Id: I9dedb918cdc19d659562f4caaf69de50a73deaff
Remove unused method _store_protocol

The _store_protocol method in
keystone.contrib.federation.backends.sql.Federation is no used,
tested, or documented, so remove it.

Change-Id: I9edf4cb36fa1f667813b4962da68a08fb277a332
Merge "Remove unused method _store_protocol"
Merge "Remove unused methods from AuthInfo"