Initialize msg with code and reason.
When reason is null, the default reason for code will be used.
When request is not null, the relevant headers will be copied to the new response message.
the status code
the status reason or null
the request that triggered the response or null
a #GstRTSPResult.
Initialize msg with code and reason.
When reason is null, the default reason for code will be used.
When request is not null, the relevant headers will be copied to the new response message.