Fix error counter - fixes #3650

For few commands, RClone counts a error multiple times. This was fixed by
creating a new error type which keeps a flag to remember if the error has
already been counted or not. The CountError function now wraps the original
error eith the above new error type and returns it.

cmd/serve/dlna/dlna_util.go

@@ -214,7 +214,7 @@ func withHeader(name string, value string, next http.Handler) http.Handler {
 
 // serveError returns an http.StatusInternalServerError and logs the error
 func serveError(what interface{}, w http.ResponseWriter, text string, err error) {
-	fs.CountError(err)
+	err = fs.CountError(err)
 	fs.Errorf(what, "%s: %v", text, err)
 	http.Error(w, text+".", http.StatusInternalServerError)
 }

cmd/serve/httplib/serve/dir.go

@@ -68,7 +68,7 @@ func (d *Directory) AddEntry(remote string, isDir bool) {
 
 // Error logs the error and if a ResponseWriter is given it writes a http.StatusInternalServerError
 func Error(what interface{}, w http.ResponseWriter, text string, err error) {
-	fs.CountError(err)
+	err = fs.CountError(err)
 	fs.Errorf(what, "%s: %v", text, err)
 	if w != nil {
 		http.Error(w, text+".", http.StatusInternalServerError)

cmd/serve/restic/restic.go

@@ -271,7 +271,7 @@ func (s *server) postObject(w http.ResponseWriter, r *http.Request, remote strin
 
 	_, err := operations.RcatSize(r.Context(), s.f, remote, r.Body, r.ContentLength, time.Now())
 	if err != nil {
-		accounting.Stats(r.Context()).Error(err)
+		err = accounting.Stats(r.Context()).Error(err)
 		fs.Errorf(remote, "Post request rcat error: %v", err)
 		http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)