Description of problem:
  Target VM failed to enter running status after migration with persistent bitmap on shared storage

Version-Release number of selected component (if applicable):
  kernel version:3.10.0-1041.el7.x86_64
  qemu-kvm-rhev version:qemu-kvm-rhev-2.12.0-27.el7.x86_64

How reproducible:
 100%

Steps to Reproduce:
1.Start src guest with qemu cmds:
    /usr/libexec/qemu-kvm \
    -name 'avocado-vt-vm1' \
    -machine pc  \
    -nodefaults \
    -device VGA,bus=pci.0,addr=0x2  \
    -chardev socket,id=qmp_id_qmpmonitor1,path=/var/tmp/monitor-qmpmonitor1-20190123-032240-rOoB4cgD,server,nowait \
    -mon chardev=qmp_id_qmpmonitor1,mode=control  \
    -chardev socket,id=qmp_id_catch_monitor,path=/var/tmp/monitor-catch_monitor-20190123-032240-rOoB4cgD,server,nowait \
    -mon chardev=qmp_id_catch_monitor,mode=control \
    -device pvpanic,ioport=0x505,id=id8Ec4Bn  \
    -chardev socket,id=serial_id_serial0,path=/var/tmp/serial-serial0-20190123-032240-rOoB4cgD,server,nowait \
    -device isa-serial,chardev=serial_id_serial0  \
    -chardev socket,id=seabioslog_id_20190123-032240-rOoB4cgD,path=/var/tmp/seabios-20190123-032240-rOoB4cgD,server,nowait \
    -device isa-debugcon,chardev=seabioslog_id_20190123-032240-rOoB4cgD,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 \
    -drive id=drive_image1,if=none,snapshot=off,aio=threads,cache=none,format=qcow2,file=/home/kvm_autotest_root/images/rhel77-64-virtio.qcow2 \
    -device virtio-blk-pci,id=image1,drive=drive_image1,bus=pci.0 \
    -device virtio-net-pci,mac=9a:39:3a:3b:3c:3d,id=id1JNQsL,vectors=4,netdev=idVpZZ6A,bus=pci.0  \
    -netdev tap,id=idVpZZ6A,vhost=on \
    -m 4096  \
    -smp 2,maxcpus=2,cores=1,threads=1,sockets=2  \
    -cpu host,+kvm_pv_unhalt \
    -device usb-tablet,id=usb-tablet1,bus=usb1.0,port=1  \
    -vnc :0  \
    -rtc base=utc,clock=host,driftfix=slew  \
    -boot order=cdn,once=c,menu=off,strict=off \
    -enable-kvm \
    -monitor stdio \
    -qmp tcp:0:3000,server,nowait \

2. In src, add a persistent bitmap.
    { "execute": "block-dirty-bitmap-add", "arguments": {"node": "drive_image1", "name": "bitmap0","persistent":true}}

3. In src, shutdown VM, then re-start it with qemu cmds in step1, query bitmap info:
   {"execute":"query-block"}
{"return": [{"io-status": "ok", "device": "drive_image1", "locked": false, "removable": false, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "image": {"virtual-size": 21474836480, "filename": "/home/kvm_autotest_root/images/rhel77-64-virtio.qcow2", "cluster-size": 65536, "format": "qcow2", "actual-size": 5626576896, "format-specific": {"type": "qcow2", "data": {"compat": "1.1", "lazy-refcounts": false, "bitmaps": [{"flags": ["in-use", "auto"], "name": "bitmap0", "granularity": 65536}], "refcount-bits": 16, "corrupt": false}}, "dirty-flag": false}, "iops_wr": 0, "ro": false, "node-name": "#block142", "backing_file_depth": 0, "drv": "qcow2", "iops": 0, "bps_wr": 0, "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, "cache": {"no-flush": false, "direct": true, "writeback": true}, "file": "/home/kvm_autotest_root/images/rhel77-64-virtio.qcow2", "encryption_key_missing": false}, "qdev": "/machine/peripheral/image1/virtio-backend", "dirty-bitmaps": [{"name": "bitmap0", "recording": true, "persistent": true, "busy": false, "status": "active", "granularity": 65536, "count": 10682368}], "type": "unknown"}]}

4.In src, set bitmap migration state to "true"
   {"execute":"migrate-set-capabilities","arguments":{"capabilities":[{"capability":"events","state":true},{"capability":"dirty-bitmaps","state":true}]}}

5.Start dst vm with qemu cmds:
   /usr/libexec/qemu-kvm \
    -name 'avocado-vt-vm1' \
    -machine pc  \
    -nodefaults \
    -device VGA,bus=pci.0,addr=0x2  \
    -chardev socket,id=qmp_id_qmpmonitor1,path=/var/tmp/monitor-qmpmonitor1-20190123-032240-rOoB4cgE,server,nowait \
    -mon chardev=qmp_id_qmpmonitor1,mode=control  \
    -chardev socket,id=qmp_id_catch_monitor,path=/var/tmp/monitor-catch_monitor-20190123-032240-rOoB4cgD,server,nowait \
    -mon chardev=qmp_id_catch_monitor,mode=control \
    -device pvpanic,ioport=0x505,id=id8Ec4Bn  \
    -chardev socket,id=serial_id_serial0,path=/var/tmp/serial-serial0-20190123-032240-rOoB4cgD,server,nowait \
    -device isa-serial,chardev=serial_id_serial0  \
    -chardev socket,id=seabioslog_id_20190123-032240-rOoB4cgD,path=/var/tmp/seabios-20190123-032240-rOoB4cgD,server,nowait \
    -device isa-debugcon,chardev=seabioslog_id_20190123-032240-rOoB4cgD,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 \
    -drive id=drive_image1,if=none,snapshot=off,aio=threads,cache=none,format=qcow2,file=/home/kvm_autotest_root/images/rhel77-64-virtio.qcow2 \
    -device virtio-blk-pci,id=image1,drive=drive_image1,bus=pci.0 \
    -device virtio-net-pci,mac=9a:39:3a:3b:3c:3d,id=id1JNQsL,vectors=4,netdev=idVpZZ6A,bus=pci.0  \
    -netdev tap,id=idVpZZ6A,vhost=on \
    -m 4096  \
    -smp 2,maxcpus=2,cores=1,threads=1,sockets=2  \
    -cpu host,+kvm_pv_unhalt \
    -device usb-tablet,id=usb-tablet1,bus=usb1.0,port=1  \
    -vnc :1  \
    -rtc base=utc,clock=host,driftfix=slew  \
    -boot order=cdn,once=c,menu=off,strict=off \
    -enable-kvm \
    -monitor stdio \
    -qmp tcp:0:3001,server,nowait \
    -incoming tcp:0:5000 \

6.Migrate from src to dst.
  {"execute":"migrate","arguments":{"uri":"tcp:10.73.224.68:5000"}}
  {"timestamp": {"seconds": 1557320740, "microseconds": 332801}, "event": "MIGRATION", "data": {"status": "setup"}}
{"return": {}}
{"timestamp": {"seconds": 1557320740, "microseconds": 363323}, "event": "MIGRATION_PASS", "data": {"pass": 1}}
{"timestamp": {"seconds": 1557320740, "microseconds": 363365}, "event": "MIGRATION", "data": {"status": "active"}}
{"timestamp": {"seconds": 1557320786, "microseconds": 162136}, "event": "MIGRATION_PASS", "data": {"pass": 2}}
{"timestamp": {"seconds": 1557320787, "microseconds": 62536}, "event": "MIGRATION_PASS", "data": {"pass": 3}}
{"timestamp": {"seconds": 1557320787, "microseconds": 163210}, "event": "MIGRATION_PASS", "data": {"pass": 4}}
{"timestamp": {"seconds": 1557320787, "microseconds": 164166}, "event": "STOP"}
{"timestamp": {"seconds": 1557320787, "microseconds": 164643}, "event": "MIGRATION_PASS", "data": {"pass": 5}}
{"timestamp": {"seconds": 1557320787, "microseconds": 168601}, "event": "MIGRATION", "data": {"status": "completed"}}


Actual results:
 After step6, src:
                 VM status: paused (postmigrate) status.
              dst:
                (qemu) qemu-kvm: Could not reopen qcow2 layer: Bitmap already exists: bitmap0

                (qemu) info status 
VM status: paused

So, dst vm failed to run after migration with persistent bitmap.

Expected results:
 Dst vm can enter running status after migration with persistent bitmap.