Description of problem:
Since usb-ccid controllers are formatted before usb-hubs on the QEMU command line, so guest will fail to start if plug a ccid controller on hub.

Version-Release number of selected component (if applicable):
libvirt-2.0.0-8.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1. define and edit a guest like following :
#virsh dumpxml vm2 
......
<controller type='ccid' index='0'>
      <address type='usb' bus='0' port='6.1'/>
    </controller>
  <smartcard mode='passthrough' type='spicevmc'>
      <address type='ccid' controller='0' slot='0'/>
    </smartcard>
......

2. start guest 
# virsh start vm2
error: Failed to start domain vm2
error: internal error: qemu unexpectedly closed the monitor: 2016-09-12T09:47:46.638568Z qemu-kvm: -device usb-ccid,id=ccid0,bus=usb.0,port=6.1: usb port 6.1 (bus usb.0) not found (in use?)


Actual results:
As step 2, guest with usb-ccid on hub fail to start.

Expected results:
Guest can start successfully or give some error like we cannot use it in this way.


Additional info: