Race free disconnection of a connected user with occtl

Improved user disconnection to avoid race conditions

Previously when we were disconnecting a user there were few seconds after which the cookie was still valid, so a reconnect would succeed by the same user. This change ensures that a disconnected (via occtl) user cannot re-use the same cookie to connect. That enables a safe user removal from the authentication database, and from run-time.

Resolves: #59 (closed)