qemu-attach: Assign device aliases
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1141621
    
    As part of attach processing, assign the device aliases by calling
    qemuAssignDeviceAliases during qemuDomainQemuAttach once all the devices
    are found after the qemuParseCommandLinePid processing.
    
    This will alleviate a symptom that caused a libvirtd crash during an
    attempted device detach.