Bug 1572856

Description of problem:
'block-job-cancel' can not cancel a "drive-mirror" job.
The job will keep running and get "BLOCK_JOB_READY" and "BLOCK_JOB_COMPLETED"
at last.

And this is a regression issue for RHEL7.6

Version-Release number of selected component (if applicable):
qemu: qemu-kvm-rhev-2.12.0-1.el7.x86_64
kernel: kernel-3.10.0-877.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Boot vm.
2. Execute "driver-mirror" with qmp.
{"execute": "drive-mirror", "arguments": {"mode": "absolute-paths", "format": "qcow2", "device": "drive_image1", "speed": 0, "sync": "full", "target": "/home/kvm_autotest_root/images/target1.qcow2"}}

3.Execute "block-job-cancel" with qmp.
{"execute": "block-job-cancel", "arguments": {"device": "drive_image1"}}

qmp command log:
{"execute": "drive-mirror", "arguments": {"mode": "absolute-paths", "format": 
           ^^^^^^^^^^^^^^^^^
"qcow2", "device": "drive_image1", "speed": 0, "sync": "full", "target": "/home/kvm_autotest_root/images/target1.qcow2"}}
{"return": {}}
{"execute": "query-block-jobs"}
{"return": [{"auto-finalize": true, "io-status": "ok", "device": "drive_image1", "auto-dismiss": true, "busy": true, "len": 4331208704, "offset": 417923072, "status": "running", "paused": false, "speed": 0, "ready": false, "type": "mirror"}]}
{"execute": "block-job-cancel", "arguments": {"device": "drive_image1"}}
           ^^^^^^^^^^^^^^^^^^^^
{"return": {}}
{"execute": "query-block-jobs"}
{"return": [{"auto-finalize": true, "io-status": "ok", "device": "drive_image1", "auto-dismiss": true, "busy": true, "len": 4331208704, "offset": 1353318400, 
                                                                ^^^^^^^^^^^^ 
"status": "running", "paused": false, "speed": 0, "ready": false, "type": "mirror"}]}
{"execute": "query-block-jobs"}
{"return": [{"auto-finalize": true, "io-status": "ok", "device": "drive_image1", "auto-dismiss": true, "busy": true, "len": 4331208704, "offset": 1566965760, 
                                                                ^^^^^^^^^^^^^ 
"status": "running", "paused": false, "speed": 0, "ready": false, "type": "mirror"}]}
{"execute": "query-block-jobs"}
{"return": [{"auto-finalize": true, "io-status": "ok", "device": "drive_image1", "auto-dismiss": true, "busy": true, "len": 4331208704, "offset": 3257335808, "status": "running", "paused": false, "speed": 0, "ready": false, "type": "mirror"}]}
{"timestamp": {"seconds": 1524901760, "microseconds": 253202}, "event": "BLOCK_JOB_READY", "data": {"device": "drive_image1", "len": 4331208704, 
^^^^^^^^^^^^^^^^^^
"offset": 4331208704, "speed": 0, "type": "mirror"}}
{"timestamp": {"seconds": 1524901760, "microseconds": 253509}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "drive_image1", "len": 4331208704, 
^^^^^^^^^^^^^^^^^^^^^
"offset": 4331208704, "speed": 0, "type": "mirror"}}





Actual results:
can not cancel the block job.

Expected results:
job should be cancelled, and get "BLOCK_JOB_CANCELLED" event.

Additional info:
qemu command line:
/usr/libexec/qemu-kvm \
    -S  \
    -name 'avocado-vt-vm1'  \
    -sandbox off  \
    -machine pc  \
    -nodefaults  \
    -vga qxl \
    -device pci-bridge,id=pci_bridge,bus=pci.0,addr=0x3,chassis_nr=1 \
    -device intel-hda,bus=pci.0,addr=0x4 \
    -device hda-duplex  \
    -chardev socket,id=qmp_id_qmp1,path=/var/tmp/avocado_azbh2D/monitor-qmp1-20180427-082517-cs9RLzLn,server,nowait \
    -mon chardev=qmp_id_qmp1,mode=control  \
    -chardev socket,id=qmp_id_catch_monitor,path=/var/tmp/avocado_azbh2D/monitor-catch_monitor-20180427-082517-cs9RLzLn,server,nowait \
    -mon chardev=qmp_id_catch_monitor,mode=control \
    -device pvpanic,ioport=0x505,id=idJw3ilG  \
    -chardev socket,id=serial_id_serial0,path=/var/tmp/avocado_azbh2D/serial-serial0-20180427-082517-cs9RLzLn,server,nowait \
    -device isa-serial,chardev=serial_id_serial0 \
    -device virtio-serial-pci,id=virtio_serial_pci0,bus=pci.0,addr=0x5 \
    -chardev socket,path=/var/tmp/avocado_azbh2D/virtio_port-vs-20180427-082517-cs9RLzLn,nowait,id=idyoBE6X,server \
    -device virtserialport,id=idgzmqQo,name=vs,bus=virtio_serial_pci0.0,chardev=idyoBE6X \
    -object rng-random,filename=/dev/random,id=passthrough-9bzWyTnW \
    -device virtio-rng-pci,id=virtio-rng-pci-MUWns1SF,rng=passthrough-9bzWyTnW,bus=pci.0,addr=0x6  \
    -chardev socket,id=seabioslog_id_20180427-082517-cs9RLzLn,path=/var/tmp/avocado_azbh2D/seabios-20180427-082517-cs9RLzLn,server,nowait \
    -device isa-debugcon,chardev=seabioslog_id_20180427-082517-cs9RLzLn,iobase=0x402 \
    -device ich9-usb-ehci1,id=usb1,addr=0x1d.7,multifunction=on,bus=pci.0 \
    -device ich9-usb-uhci1,id=usb1.0,multifunction=on,masterbus=usb1.0,addr=0x1d.0,firstport=0,bus=pci.0 \
    -device ich9-usb-uhci2,id=usb1.1,multifunction=on,masterbus=usb1.0,addr=0x1d.2,firstport=2,bus=pci.0 \
    -device ich9-usb-uhci3,id=usb1.2,multifunction=on,masterbus=usb1.0,addr=0x1d.4,firstport=4,bus=pci.0 \
    -device nec-usb-xhci,id=usb2,bus=pci.0,addr=0x7 \
    -device virtio-scsi-pci,id=virtio_scsi_pci0,bus=pci.0,addr=0x8 \
    -drive id=drive_image1,if=none,snapshot=off,aio=native,cache=none,format=qcow2,file=/home/kvm_autotest_root/images/rhel75-64-virtio-scsi.qcow2 \
    -device scsi-hd,id=image1,drive=drive_image1 \
    -device virtio-net-pci,mac=9a:8b:8c:8d:8e:8f,id=idcutDVH,vectors=4,netdev=idS6OpFS,bus=pci.0,addr=0x9  \
    -netdev tap,id=idS6OpFS,vhost=on \
    -m 4096  \
    -smp 8,cores=4,threads=1,sockets=2  \
    -cpu 'SandyBridge',+kvm_pv_unhalt \
    -device usb-tablet,id=usb-tablet1,bus=usb2.0,port=1  \
    -vnc :0 \
    -rtc base=utc,clock=host,driftfix=slew  \
    -boot order=cdn,once=c,menu=off,strict=off  \
    -no-hpet \
    -enable-kvm  \
    -watchdog i6300esb \
    -watchdog-action reset \
    -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0xa \
    -monitor stdio \