Comment 13 for bug 1082213

This feature appears to cause a bug.
To reproduce attach-device to a virtual machine and then stop that vm
Start another vm and try to attach-device to that machine
I get:
virsh attach-device vm1 /var/lib/libvirt/hotplug/usb-serial.xml
error: Failed to attach device from /var/lib/libvirt/hotplug/usb-serial.xml
error: Requested operation is not valid: USB device 002:005 is in use by domain ..

usb-serial:
    <hostdev mode='subsystem' type='usb' managed='yes'>
      <source>
        <vendor id='0x067b'/>
        <product id='0x2303'/>
      </source>
    </hostdev>

backing up libvirt0 and libvirt-bin to 0.9.8-2ubuntu17.7 makes this problem go away.

While looking at this I found a Fedora bug that looks similar. The upstream patches they identified may be of interest.
https://bugzilla.redhat.com/show_bug.cgi?id=814866