[PATCH] docs/block-replication.txt: Fix replication top-id command demo

[Zhang Chen]

This demo not correct, the original childs1 can't pass the
the bdrv_is_root_node check in replcation_start().
Keep consistent with docs/COLO-FT.txt

Signed-off-by: Zhang Chen <chen.zhang@intel.com>
---
 docs/block-replication.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/block-replication.txt b/docs/block-replication.txt
index 108e9166a8..66ad540676 100644
--- a/docs/block-replication.txt
+++ b/docs/block-replication.txt
@@ -179,7 +179,7 @@ Primary:
 
 Secondary:
   -drive if=none,driver=raw,file.filename=1.raw,id=colo1 \
-  -drive if=none,id=childs1,driver=replication,mode=secondary,top-id=childs1
+  -drive if=none,id=childs1,driver=replication,mode=secondary,top-id=top-disk1
          file.file.filename=active_disk.qcow2,\
          file.driver=qcow2,\
          file.backing.file.filename=hidden_disk.qcow2,\
-- 
2.25.1