there are 3 phases of authentication and authorization in cephx:
0. proto = CEPH_AUTH_UNKNOWN, for start the session,
create auth handlers on both sides.
1. GET_AUTH_SESSION_KEY, to get authenticated, the client will
get the session ticket at the end of this phase. the session ticket,
is actually also a service ticket for CEPH_ENTITY_TYPE_AUTH.
2. CEPHX_GET_PRINCIPAL_SESSION_KEY, to get authorized, the client
will get the requested, service tickets at the end of this phase.
Signed-off-by: Kefu Chai <kchai@redhat.com>
