add log_file option to kubelet flags

Change-Id: I5e75902739e2f869244d1b8b229be2580aca8149

cmd/kubelet/app/options/globalflags.go

@@ -104,6 +104,7 @@ func addGlogFlags(fs *pflag.FlagSet) {
 	register(global, local, "vmodule")
 	register(global, local, "log_backtrace_at")
 	register(global, local, "log_dir")
+	register(global, local, "log_file")
 
 	fs.AddFlagSet(local)
 }