Get endpoint urls for all CLI operations
Refs: #3874 Use kamaki.clients.astakos.AstakosClient as a cached astakos client to get user information and, most importantly, endpoints. Allow users to authenticate multiple tokens on the same session. In every session there must be at most one authentication per user/token. Major change: top kamaki.cli.commands class now contains a base_auth field with the cached authenticating client. All urls are drained from this field.