etcdmain: use embed.DefaultLogOutput for flags

Signed-off-by: Gyu-Ho Lee <gyuhox@gmail.com>

etcdmain/config.go

@@ -192,7 +192,7 @@ func newConfig() *config {
 	// logging
 	fs.BoolVar(&cfg.Debug, "debug", false, "Enable debug-level logging for etcd.")
 	fs.StringVar(&cfg.LogPkgLevels, "log-package-levels", "", "Specify a particular log level for each etcd package (eg: 'etcdmain=CRITICAL,etcdserver=DEBUG').")
-	fs.StringVar(&cfg.LogOutput, "log-output", "default", "Specify 'stdout' or 'stderr' to skip journald logging even when running under systemd.")
+	fs.StringVar(&cfg.LogOutput, "log-output", embed.DefaultLogOutput, "Specify 'stdout' or 'stderr' to skip journald logging even when running under systemd.")
 
 	// unsafe
 	fs.BoolVar(&cfg.ForceNewCluster, "force-new-cluster", false, "Force to create a new one member cluster.")