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
Signed-off-by: Nikos Mavrogiannopoulos <n.mavrogiannopoulos@gmail.com>