Description of problem:
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QMP returns error when mirroring + streaming

Version-Release number of selected component (if applicable):
--------------------------------------------------------------
scratch build:
kvm-Live-block-copy-Fix-mirroring.patch based on 265

*note: 266rhev including this patch fails to be build in brew, seems short of package in brew server repo, so i can not provide a scratch build package.

How reproducible:
-------------------
1/1

Steps to Reproduce:
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1.boot guest with:
qemu-system-x86_64 -enable-kvm -M rhel6.3.0 -m 4G -name rhel6.3-64 -rtc base=utc,clock=host,driftfix=slew -no-kvm-pit-reinjection -uuid 3f2ea5cd-3d29-48ff-aab2-23df1b6ae213 -drive file=/root/src/RHEL-Server-6.3-64-virtio.qcow2,cache=none,if=none,rerror=stop,werror=stop,id=drive-virtio-disk0,format=qcow2 -device ide-drive,drive=drive-virtio-disk0,id=device-virtio-disk0 -netdev tap,script=/etc/qemu-ifup,id=netdev0 -device virtio-net-pci,netdev=netdev0,id=device-net0 -boot order=cd -monitor stdio -usb -device usb-tablet,id=input0 -chardev socket,id=s1,path=/tmp/s1,server,nowait -device isa-serial,chardev=s1 -vnc :10 -monitor tcp::1234,server,nowait -smp 4 -qmp tcp:0:5555,server,nowait

2.
{"execute": "qmp_capabilities"}
{"return": {}}
{ "execute": "__com.redhat_drive-mirror", "arguments": { "device":
"drive-virtio-disk0", "target": "/root/sn1", "format": "qcow2"} }
{"return": {}}
{ "execute": "block_stream", "arguments": { "device": "drive-virtio-disk0" } }
{"return": {}}
{"return": {}}
{"error": {"class": "QMPExtraInputObjectMember", "desc": "QMP input object member 'return' is unexpected", "data": {"member": "return"}}}

3. although there is an error, info block-jobs shows streaming is activated.


Additional info:
-----------------
Hi, Marcelo, Kevin is on PTO, could you have a look at this?