Prometheus Blackbox exporter config doesn't handle Pulp with TLS

When pulp is deployed with TLS, the certificate is not available in the prometheus containers. As such, it will fail to reach the pulp status.

```
[prometheus@controller0 /]$ curl https://pulp-on-the-seed.co.uk/pulp/api/v3/status/
curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: https://curl.se/docs/sslcerts.html
```

