config: Accept more address format + unit test (#3915)

checkURL() is a generic function to check if a passed address
is valid. This commit adds support for addresses like `m1`
and `172.16.3.1` which is needed in MySQL and NATS. This commit
also adds tests.

cmd/notify-elasticsearch.go

@@ -37,7 +37,7 @@ func (e *elasticSearchNotify) Validate() error {
 	if !e.Enable {
 		return nil
 	}
-	if _, err := checkNetURL(e.URL); err != nil {
+	if _, err := checkURL(e.URL); err != nil {
 		return err
 	}
 	return nil