OCSP status about ssl_exporter

[ribbybibby]

Thanks for reporting this issue.

Looks like this happens because:

1. We register the metrics, even when there is no ocsp response.
2. The default value for the status metric is 0, which is also the 'Good' response

See: https://github.com/ribbybibby/ssl_exporter/blob/master/prober/metrics.go#L206-L217.

Perhaps we shouldn't register the metrics if we don't have an OCSP response.

On reflection, I wonder whether I should have made the OCSP functionality a module option and then we could fail if there is no ocsp response.

[ribbybibby]

The ssl_ocsp_response_stapled metric can be used to check whether there was a response at all.

For instance, you could check for a non-good status, but only where there is a stapled response with something like:

ssl_ocsp_response_stapled == 1 and ssl_ocsp_response_status != 0