otel-cli exec does not report a span if the command failed

[parsonsmatt]

$ otel-cli exec -- false

The above example does not report a span. If I run with --verbose, then I see this:

$ otel-cli exec --verbose -- false
2023/08/30 18:36:07 command failed: exit status 1

I think the issue is here:

	if err := child.Run(); err != nil {
		config.SoftFail("command failed: %s", err)
	}
	span.EndTimeUnixNano = uint64(time.Now().UnixNano())

	ctx, err := otlpclient.SendSpan(ctx, client, config, span)
	if err != nil {
		config.SoftFail("unable to send span: %s", err)
	}

Calling config.SoftFail is going to exit immediately. What is probably intended instead is to record the span with an error code.

[tobert]

Yep, the first config.SoftFail is the problem. My bad. If we get the test in your PR working, it'll make sure this doesn't revert.