volume: get metrics configuration from master

fix https://github.com/chrislusf/seaweedfs/issues/1354

weed/command/s3.go

@@ -152,6 +152,8 @@ func (s3opt *S3Options) startS3Server() bool {
 			break
 		}
 	}
+
+	glog.V(0).Infof("s3 server sends metrics to %s every %d seconds", metricsAddress, metricsIntervalSec)
 	if metricsAddress != "" && metricsIntervalSec > 0 {
 		go stats_collect.LoopPushingMetric("s3", stats_collect.SourceName(uint32(*s3opt.port)), stats_collect.S3Gather, metricsAddress, metricsIntervalSec)
 	}