net/http: Fix http.Get() with port specification

[sago35]

This PR corrects the behavior of http.Get(). Only http is affected, not https.

Two items were corrected.

1. Change to pass only hostname to net.ParseIP
2. Fix Port setting was always 80

[sago35]

Before the correction, addresses such as http://hostname:8088/ were not accessible.

For example, the following is a std-Go program that listens for 8088, but could not connect to

package main

import (
    "fmt"
    "log"
    "net/http"
)

var (
    ip   = ""
    port = 8088
    cnt  = 0
)

func handler(w http.ResponseWriter, req *http.Request) {
    cnt++
    fmt.Fprintf(w, "hello %d\n", cnt)
    fmt.Printf("%d %#v\n", cnt, req.UserAgent())
}

func main() {
    http.HandleFunc("/", handler)
    fmt.Printf("listen: %s:%d\n", ip, port)
    log.Fatal(http.ListenAndServe(fmt.Sprintf("%s:%d", ip, port), nil))
}

[deadprogram]

Thanks for the fix @sago35 now merging.