Add slow-start to upstream server

[isaachawley]

Made a simple main.go to test, then view the result by curling the api.

package main

import "fmt"
import "net/http"
import "github.com/nginxinc/nginx-plus-go-sdk/client"

func main() {
        httpClient := &http.Client{}
        c, err := client.NewNginxClient(httpClient, "http://127.0.0.1:8080/api")
        if err != nil {
                fmt.Println("Can't create nginx client")
        }
        server := client.UpstreamServer{
                Server:    "1.2.3.5:8080",
                SlowStart: "100s",
        }
        err = c.AddHTTPServer("test", server)
        fmt.Println(err)
        fmt.Println("vim-go")
}

[pleshakov]

@isaachawley could you add a similar this test to TestClient? We just need to add an upstream server with the slow_start value, then retrieve it and check that the slow start param is the same?

[isaachawley]

New test case is in, @pleshakov anything else?