Revert "Atomic overlay file application in wwclient"

This reverts commit 9f11b4a2b9.

cmd/wwclient/main.go

@@ -13,6 +13,7 @@ func main() {
 
 	err := root.Execute()
 	if err != nil {
+		fmt.Fprintf(os.Stderr, "ERROR: %s\n", err)
 		if wwclient.DebugFlag {
 			fmt.Printf("\nSTACK TRACE: %+v\n", err)
 		}