Rewrite "-drive" using "-blockdev/-device"

[Derek Su]

Hi,

I tried to rewrite the "-drive" command-line using "-blockdev/-device"

"-drive" command-line
```
#-drive 
if=none,id=childs0,driver=replication,mode=secondary,file.driver=qcow2,top-id=colo-disk0,file.file.filename=${folder}/secondary-active.qcow2,file.backing.driver=qcow2,file.backing.file.filename=${folder}/secondary-hidden.qcow2,file.backing.backing=parent0
\
#-drive 
if=virtio,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-threshold=1,children.0=childs0
\
```

 "-blockdev/-device" command-line
```
-blockdev '{"node-name": "parent0", "driver": "qcow2", "file":
{"driver": "file", "filename": "'${folder}/secondary.qcow2'"}}' \
-blockdev '{"node-name": "childs0", "driver": "replication", "mode":
"secondary", "top-id": "colo-disk0", "file": { "driver": "qcow2",
"file": {"driver": "file", "filename":
"'${folder}/secondary-active.qcow2'"}, "backing": {"driver": "qcow2",
"file": { "driver": "qcow2", "file": { "driver": "file", "filename":
"'${folder}/secondary-hidden.qcow2'"}}, "backing": "parent0" }}}' \
-blockdev '{"driver": "quorum", "node-name": "colo-disk0",
"read-pattern": "fifo", "vote-threshold": 1, "children": [{"driver":
"replication", "file": "childs0", "mode": "secondary"}]}' \
```


The second ( "-blockdev/-device") shows the error
```
qemu-system-x86_64: -blockdev {"node-name": "childs0", "driver":
"replication", "mode": "secondary", "top-id": "colo-disk0", "file": {
"driver": "qcow2", "file": {"driver": "file", "filename":
"/tmp/ramdisk/secondary-active.qcow2"}, "backing": {"driver": "qcow2",
"file": { "driver": "qcow2", "file": { "driver": "file", "filename":
"/tmp/ramdisk/secondary-hidden.qcow2"}}, "backing": "parent0" }}}:
Could not open backing file: Image is not in qcow2 format
```

Any errors in the rewritten version?
Thanks.

Regards,
Derek