Fix healthcheck script to check for BadRequest Status (minio#7537)

As a part of minio#7302, MinIO server's (configured with https) response when it
encounters http request has changed from 403 to 400 and the custom message
"SSL Required" is removed.

Accordingly healthcheck script is updated to check for status 400 before
trying https request.

Fixes minio#7517

dockerscripts/healthcheck.go

@@ -21,7 +21,6 @@ import (
 	"crypto/tls"
 	"errors"
 	"fmt"
-	"io/ioutil"
 	"log"
 	"net/http"
 	"net/url"
@@ -142,18 +141,10 @@ func main() {
 			// exit with success
 			os.Exit(0)
 		}
-		bodyBytes, err := ioutil.ReadAll(resp.Body)
-		if err != nil {
-			// Drain any response.
-			xhttp.DrainBody(resp.Body)
-			// GET failed exit
-			log.Fatalln(err)
-		}
-		bodyString := string(bodyBytes)
 		// Drain any response.
 		xhttp.DrainBody(resp.Body)
-		// This means sever is configured with https
-		if resp.StatusCode == http.StatusForbidden && bodyString == "SSL required" {
+		// 400 response may mean sever is configured with https
+		if resp.StatusCode == http.StatusBadRequest {
 			// Try with https
 			u.Scheme = "https"
 			resp, err = client.Get(u.String())