Fix unexpected permission error on an IPv6 configured machine (#176)

when visiting the webui.

When net.SplitHostPort is called, it will return the string "::1",
but the code was only checking for "[::1]".

internal/driver/webui.go

 }
 
 func isLocalhost(host string) bool {
-	for _, v := range []string{"localhost", "127.0.0.1", "[::1]"} {
+	for _, v := range []string{"localhost", "127.0.0.1", "[::1]", "::1"} {
 		if host == v {
 			return true
 		}

internal/driver/webui_test.go

 import (
 	"fmt"
 	"io/ioutil"
+	"net"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
 		})
 	}
 }
+
+func TestIsLocalHost(t *testing.T) {
+	for _, s := range []string{"localhost:10000", "[::1]:10000", "127.0.0.1:10000"} {
+		host, _, err := net.SplitHostPort(s)
+		if err != nil {
+			t.Error("unexpected error when splitting", s)
+			continue
+		}
+		if !isLocalhost(host) {
+			t.Errorf("host %s from %s not considered local", host, s)
+		}
+	}
+}