Curl transport host_unreachable_exceptions should potentially include more errors

[mikebaldry]

We sometimes see these 2 errors pop up:
Curl::Err::GotNothingError
Curl::Err::RecvError

It would be great to retry them as they don't happen for any particular reason I can see and its very temporary.

[karmi]

So, what should we do, add it to Elasticsearch::Transport::Transport::HTTP::Curb::host_unreachable_exceptions?

[mikebaldry]

Yeah, I see a Curl::Err::SendError once in a while too that could be retried.

I was just more putting the idea out there. I don't know if there is a reason why not to retry these?

If you're happy, I'll PR.

[karmi]

I don't remember seeing these with Curb, on the other hand, they look like safe ones to retry, so I think you can just send the PR with these added...

[mikebaldry]

Ok cheers

[karmi]

Michael, finally merged this, sorry for the holdup!