Add url tag only if not already set

plugins/inputs/http/http.go

@@ -24,9 +24,6 @@ type HTTP struct {
 	Username string
 	Password string
 
-	// Option to add "url" tag to each metric
-	TagURL bool `toml:"tag_url"`
-
 	// Path to CA file
 	SSLCA string `toml:"ssl_ca"`
 	// Path to host cert file
@@ -183,7 +180,7 @@ func (h *HTTP) gatherURL(
 	}
 
 	for _, metric := range metrics {
-		if h.TagURL {
+		if !metric.HasTag("url") {
 			metric.AddTag("url", url)
 		}
 		acc.AddFields(metric.Name(), metric.Fields(), metric.Tags(), metric.Time())