Fix linting error with string conversion

Author: duckpuppy

ultradns/resource_ultradns_dirpool.go

@@ -584,7 +584,7 @@ func hashIPInfoIPs(v interface{}) int {
 	buf.WriteString(fmt.Sprintf("%s-", m["start"].(string)))
 	buf.WriteString(fmt.Sprintf("%s-", m["end"].(string)))
 	buf.WriteString(fmt.Sprintf("%s-", m["cidr"].(string)))
-	buf.WriteString(fmt.Sprintf("%s", m["address"].(string)))
+	buf.WriteString(m["address"].(string))
 
 	h := hashcode.String(buf.String())
 	log.Printf("[DEBUG] hashIPInfoIPs(): %v -> %v", buf.String(), h)