Display better output errors

There are a couple of places where the go representation of an error is displayed. This hides the issue that's raising the error to the end user.

In my case, I'm seeing this issue:

```
Can not send metricas to newrelic: &url.Error{Op:"Post", URL:"https://platform-api.newrelic.com/platform/v1/metrics", Err:(*net.OpError)(0xc2080fc0c0)}
```

This PR modifies the log to display this:

```
Can not send metricas to newrelic: Post https://platform-api.newrelic.com/platform/v1/metrics: dial tcp: lookup platform-api.newrelic.com: no such host
```