- fixed and consolitate the duplicated code for sending the
CLOSE_REQUEST_PDU to the server into dvcman_close_channel
- call dvcman_close_channel if a dynamic channel plugin fails
to process the received channel data
- rdpegfx: don't try to remove a non-existing cache entry,
return an error instead which now will close the channel, as
expected by Microsoft's windows protocols test suite
17e0d25104