The upstream fasthttp may contain issues like 996610f021 ,
plus a code that isn't used by VictoriaMetrics. So let's use a private copy under our control instead.
This should fix the following error:
the server closed connection before returning the first response byte. Make sure the server returns 'Connection: close' response header before closing the connection
This should prevent from the following unexpected side-effects of idempotent request retries:
- increased actual timeout when scraping the target comparing to the configured scrape_timeout
- increased load on the target
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/357
