Add the http2 GOAWAY error to IsProbableEOF for ignoring in watch

[smarterclayton]

http2 is allowed to tell us to go away, and for watch it is safe to exit and restart in almost all cases where a connection is forcibly closed by the upstream. This error message happens a lot behind ELB and other http2 aware proxies.

Treat the error as "basically done" as suggested by: golang/go#18639 (comment)

Otherwise, we log at V(0) which shows up in command line tools, scripting, etc and is totally not actionable.

For instance, in a CLI tool using watch.Until against an apiserver behind AWS ELB:

level=info msg="Waiting up to 30m0s for the bootstrap-complete event..."
E0124 06:00:48.845920      29 streamwatcher.go:109] Unable to decode an event from the watch stream: http2: server sent GOAWAY and closed the connection; LastStreamID=3, ErrCode=NO_ERROR, debug=""

/kind bug

When a watch is closed by an HTTP2 load balancer and we are told to go away, skip printing the message to stderr by default.

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[liggitt]

/lgtm

this also would affect this code path:

kubernetes/staging/src/k8s.io/client-go/rest/request.go

Lines 582 to 589 in 2cd8825

	if err != nil {
	// The watch stream mechanism handles many common partial data errors, so closed
	// connections can be retried in many cases.
	if net.IsProbableEOF(err) {
	return watch.NewEmptyWatch(), nil
	}
	return nil, err
	}

given the other network errors that were triggering the code path, that seems reasonable

is there any way to test this to catch message drift?

[fedebongio]

/assign @roycaihw

[fedebongio]

/cc @wenjiaswe