colo-compare: Update the COLO document to add the IOThread configuration

Update colo-proxy.txt,add IOThread configuration.
Later we have to configure IOThread,if not COLO can not work.
Reviewed-by: NZhang Chen <zhangchen.fnst@cn.fujitsu.com>
Signed-off-by: NWang Yong <wang.yong155@zte.com.cn>
Signed-off-by: NWang Guang <wang.guang55@zte.com.cn>
Signed-off-by: NJason Wang <jasowang@redhat.com>

docs/colo-proxy.txt

@@ -170,10 +170,11 @@ Primary(ip:3.3.3.3):
 -chardev socket,id=compare0-0,host=3.3.3.3,port=9001
 -chardev socket,id=compare_out,host=3.3.3.3,port=9005,server,nowait
 -chardev socket,id=compare_out0,host=3.3.3.3,port=9005
+-object iothread,id=iothread1
 -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
 -object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
 -object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
--object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0
+-object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,iothread=iothread1
 
 Secondary(ip:3.3.3.8):
 -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,down script=/etc/qemu-ifdown