[CODE] ddns: add option to silence all output

README.md

@@ -49,6 +49,9 @@ Mandatory variables:
 - `ddns_passphrase`: Passphrase for updating dynDNS entries
 - `ddns_domain`: Domain where the host's entries are created as `$hostname.$ddns_domain`
 
+Optional variable:
+- `ddns_silence`: Set to true to silence stderr too
+
 ### Telegraf
 Mandatory variables:
 - `telegraf_server_url`: URL of the influxDB server, e.g. `https://example.com:8086`