Hardening/libcurl

**DON'T MERGE**

Orion uses libcurl to send HTTP requests.
Considering alarmas described at https://forge.fi-ware.org/plugins/mediawiki/wiki/fiware/index.php/Publish/Subscribe_Broker_-_Orion_Context_Broker_-_Installation_and_Administration_Guide#Alarm_conditions I would suggest to change the text to the following one:

```
Notification failure for %s:%s (curl_easy_perform failed: %s)
```
where first and second %s correspond to IP and port.

I understand tha the "\n" is not really needed, or I'm wrong?