CA and Bearer Token are config of `kubernetes_sd_configs`, not the
`scrape_config`. Also updated misleading top-level comment and removed
unnecessary global config.
* Support multiple masters with retries against each master as required.
* Scrape masters' metrics.
* Add role meta label for node/service/master to make it easier for relabeling.
Keegan Carruthers-Smith
Jimmi Dyson