例如在PUT的时候，加入If-Modified-Since参数，返回501 Not Implemented错误

请求示例：

PUT /bucket/my-image.jpg HTTP/1.1
Host: storage.aliyun.com
Date: Wed, 28 May 2011 22:32:00 GMT
If-Modified-Since: Wed, 06 Apr 2011 10:02:46 GMT

返回消息头示例:

501 Not Implemented
x-oss-request-id: 77E534EBF90372BE
Content-Type: application/xml
Transfer-Encoding: chunked
Date: Thu, 28 Apr 2011 08:03:07 GMT
Connection: close
Server: AliyunOSS

返回消息体示例:

<?xml version="1.0" ?>
<Error>
	<Code>
		NotImplemented
	</Code>
	<Message>
		A header you provided implies functionality 
		that is not implemented.
	</Message>
	<Header>
		If-Modified-Since
	</Header>
	<RequestId>
		77E534EBF90372BE
	</RequestId>
	<HostId>
		storage.aliyun.com
	</HostId>
</Error>