No data when exporter started without beat

[michael-doubez]

When the beat exporter is started but the beat (filebeat in my case) start failed, the exporter doesn't send back any data.

I would have expected to get the usual exporter internal metrics and a filebeat_up set to 0.
As it is, I have aggregate the up{job="beat"} == 0 and filebeat_up == 0 to have a unified view.

It is not a deal breaker but it would make querying easier.

[michael-doubez]

I see in the code that it is because you are using he beat type to generate metric name.