Description of problem:
RNG device didn't deleted when ran command: "device_del virtrng0" in monitor at the first time


Version-Release number of selected component (if applicable):
kernel version:2.6.32-595.el6.x86_64
qemu-img-0.12.1.2-2.482.el6.x86_64
guest: rhel6


How reproducible:
3/3

Steps to Reproduce:
1: Boot vm with following cli:

/usr/libexec/qemu-kvm \
-name rhel6 \
-machine rhel6.6.0,accel=kvm \
-realtime mlock=off \
-cpu SandyBridge \
-m 6G   \
-smp 4,cores=2,threads=1,sockets=2  \
-uuid 49a3438a-70a3-4ba8-92ce-3a05e0934608 \
-nodefaults \
-rtc base=utc,driftfix=slew \
-monitor unix:/tmp/monitor-unix,server,nowait \
-global kvm-pit.lost_tick_policy=discard \
-global PIIX4_PM.disable_s3=1 \
-global PIIX4_PM.disable_s4=1 \
-boot order=c,menu=on,strict=on \
-device usb-ehci,id=ehci \
-drive file=/home/usb/storage.qcow2,if=none,id=storage1,format=qcow2 \
-device usb-storage,drive=storage1,bus=ehci.0 \
-drive file=/home/usb/rhel6.img,if=none,id=ide,media=disk,cache=none,format=raw \
-device ide-drive,drive=ide,id=ide0 \
-cdrom /usr/share/virtio-win/virtio-win.iso \
-netdev tap,id=hostnet1  \
-device e1000,netdev=hostnet1,id=virtio-net-pci1,mac=b6:2f:a8:85:72:6c,bus=pci.0,multifunction=off \
-monitor stdio \
-qmp tcp:0:4466,server,nowait -serial unix:/tmp/ttym,server,nowait \
-vga qxl \
-spice port=5910,addr=0.0.0.0,disable-ticketing,seamless-migration=on \
-object rng-random,filename=/dev/urandom,id=rng0 \
-device virtio-rng-pci,rng=rng0,id=virtrng0 \
-k en-us \

2. Monitor command: "device_del virtrng0"
3. Check the rng device through monitor command "info pci"

Actual results:
the RNG device didn't deleted, we must executed monitor command: "device_del virtrng0" again and the device should be deleted

Expected results:
the RNG device should be deleted when executed monitor command: "device_del virtrng0" at the first time.

Additional info: