boxes default USB config incorrectly adds some devices as USB1
See the attached XML. This is a Fedora 28 VM created with boxes, on Fedora 28 host. For this config, boxes adds 8 USB devices:
- USB tablet, USB mouse, USB keyboard
- USB CCID reader
- 4 USB redirdevs
However the default USB config only has 6 USB2 ports. In this case, when libvirt/qemu sees a 6th device added, it automatically adds a usb1.1 hub into the last port, and attaches the 6th device into the hub. Devices 7 and 8 get added as well. This behavior is obviously subtle and not very desireable but we are kinda stuck with it for compat reasons. Plus I don't think qemu supports any other type of hub. This behavior might be responsible for some of the other USB bugs in the tracker...