private void changeStatus(AgentStatus status) {
        this.agentStatus = status;
        if (logger.isDebugEnabled()) {
            logger.debug("Agent status is changed. {}", status);
        }
    }
@author emeroad
@author koo.taejin
@author hyungil.jeong
agent-module/profiler/src/main/java/com/navercorp/pinpoint/profiler/DefaultAgent.java