http Agent: Honor retries on read timeouts

[puerco]

At present, the http agent will honor the retries setting when sending the http request to the server:

release-utils/http/agent.go

Lines 163 to 169 in 7e56f68

	func (a *Agent) GetRequest(u string) (response *http.Response, err error) {
	logrus.Debugf("Sending GET request to %s", u)
	return a.retryRequest(func() (*http.Response, error) {
	return a.SendGetRequest(a.Client(), u)
	})
	}

This means that errors in the connection or from http status codes are retried. But after returning the request object, timeouts reading the response body will cause the agent to return an error immediately instead of honoring the retries setting.

/kind bug