Scraper label names are converted to lowercase

[Geoffrey Guilbon]

Scraper labels are converted into a lowercase metrics:
Here podName will become podname

  10.100.2.14:9100:
    url: http://10.100.2.14:9100/metrics
    period: 1m0s
    format: prometheus
    labels:
      host: 10.100.2.14
      podName: mypod
      podNamespace: mynamespace
      port: "9100"