public void stop() {
        // Cancel executions of running commands
        sessions.clear();
        sessionsCounter.clear();
    }
Releases the data kept for the command execution whose id is sessionid. The number of
commands executions currently being executed by the user (full JID) will be decreased.

@param sessionid id of the session that identifies this command execution.
@param from the full JID of the command requester.
xmppserver/src/main/java/org/jivesoftware/openfire/commands/AdHocCommandManager.java