[CA-151657] Increase speed of dpriv to guest agent clipboard copying
[CA-151657] Increase speed of dpriv to guest agent clipboard copying

By increasing buffer sizes for communications between client and agent

Signed-off-by: Ben Chalmers <b3747009c0bd3b0a8ac423a403e103e776512006@citrix.com>

cheng-z/win-xenguestagent,xenserver/win-xenguestagent,kostaslamda/win-xenguestagent,cheng--zhang/win-xenguestagent,cheng-z/win-xenguestagent,cheng--zhang/win-xenguestagent,cheng--zhang/win-xenguestagent,cheng-z/win-xenguestagent,kostaslamda/win-xenguestagent,xenserver/win-xenguestagent