go: Replace Logrus with go-logging.

go/src/infra/libs/logging/appengine.go

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // +build appengine
 
 package logging
 
 type nullLogger struct{}
 
 func (*nullLogger) Infof(string, ...interface{})    {}
 func (*nullLogger) Warningf(string, ...interface{}) {}
 func (*nullLogger) Errorf(string, ...interface{})   {}
 
 func init() {
         DefaultLogger = &nullLogger{}
-        IsTerminal = false
 }