accounting: fix global error acounting

fs.CountError is called when an error is encountered. The method was
calling GlobalStats().Error(err) which incremented the error at the
global stats level. This led to calls to core/stats with group= filter
returning an error count of 0 even if errors actually occured.

This change requires the context to be provided when calling
fs.CountError. Doing so, we can retrieve the correct StatsInfo to
increment the errors from.

Fixes #5865

fs/accounting/accounting.go

@@ -44,7 +44,9 @@ func Start(ctx context.Context) {
 	//
 	// We can't do this in an init() method as it uses fs.Config
 	// and that isn't set up then.
-	fs.CountError = GlobalStats().Error
+	fs.CountError = func(ctx context.Context, err error) error {
+		return Stats(ctx).Error(err)
+	}
 }
 
 // Account limits and accounts for one transfer