private AgentLifeCycleState getAgentLifeCycleState(AgentStatus agentStatus) {
        if (agentStatus != null) {
            return agentStatus.getState();
        } else {
            return AgentLifeCycleState.UNKNOWN;
        }
    }
@author netspider
@author emeroad
@author HyunGil Jeong
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/nodes/ServerInstance.java