update 优化 sky-agent 默认开启即使连不上服务端也跟踪配置

(有些人就爱这么用)

docker/skywalking/agent/config/agent.config

@@ -68,7 +68,7 @@ agent.force_reconnection_period=${SW_AGENT_FORCE_RECONNECTION_PERIOD:1}
 agent.operation_name_threshold=${SW_AGENT_OPERATION_NAME_THRESHOLD:150}
 
 # Keep tracing even the backend is not available if this value is true.
-agent.keep_tracing=${SW_AGENT_KEEP_TRACING:false}
+agent.keep_tracing=${SW_AGENT_KEEP_TRACING:true}
 
 # The agent use gRPC plain text in default.
 # If true, SkyWalking agent uses TLS even no CA file detected.