minio-browser: do not redirect to /minio if MINIO_BROWSER=off (#2863)

fixes #2837

cmd/generic-handlers.go

@@ -18,6 +18,7 @@ package cmd
 
 import (
 	"net/http"
+	"os"
 	"path"
 	"regexp"
 	"strings"
@@ -76,6 +77,7 @@ func setBrowserRedirectHandler(h http.Handler) http.Handler {
 }
 
 func (h redirectHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if !strings.EqualFold(os.Getenv("MINIO_BROWSER"), "off") {
 		// Re-direction handled specifically for browsers.
 		if strings.Contains(r.Header.Get("User-Agent"), "Mozilla") && !isRequestSignatureV4(r) {
 			// '/' is redirected to 'locationPrefix/'
@@ -89,6 +91,8 @@ func (h redirectHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 				return
 			}
 		}
+	}
+
 	h.handler.ServeHTTP(w, r)
 }