Incorrect CloudKitty prometheus_url

[Pierre Riteau]

The prometheus_url configuration value generated for CloudKitty doesn't point to the HTTP API:

2022-02-21 16:55:38.306 59 ERROR cloudkitty.orchestrator [-] [scope: 581ceb9870f749eeab57efb12b378756, worker: 4] Error while collecting metric volume.size at timestamp 2022-02-01 00:00:00+00:00: Could not get a valid json response for http://local.prometheus.example:9091/query?query=max%28max_over_time%28volume.size%7Bproject_id%3D%22581ceb9870f749eeab57efb12b378756%22%7D%5B3600s%5D%29%29+by+%28id%2C+tenant_id%2C+project_id%29&time=2022-02-01T01%3A00%3A00%2B00%3A00 (response: 404 page not found). Exiting.: cloudkitty.collector.exceptions.CollectError: Could not get a valid json response for http://local.prometheus.example:9091/query?query=max%28max_over_time%28volume.size%7Bproject_id%3D%22581ceb9870f749eeab57efb12b378756%22%7D%5B3600s%5D%29%29+by+%28id%2C+tenant_id%2C+project_id%29&time=2022-02-01T01%3A00%3A00%2B00%3A00 (response: 404 page not found