OSS参数不支持的操作

　　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/1.1Host: storage.aliyun.comDate: Wed, 28 May 2011 22:32:00 GMTIf-Modified-Since: Wed, 06 Apr 2011 10:02:46 GMT

　　返回消息头示例:

　　501 Not Implementedx-oss-request-id: 77E534EBF90372BEContent-Type: application/xmlTransfer-Encoding: chunkedDate: Thu, 28 Apr 2011 08:03:07 GMTConnection: closeServer: 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>