virt-aa-helper: fix libusb access to udev usb descriptions
    
    In bf3a4140 "virt-aa-helper: fix libusb access to udev usb data" the
    libusb access to properly detect the device/bus ids was fixed.
    
    The path /run/udev/data/+usb* contains a subset of that information we
    already allow to be read and are currently not needed for the function
    qemu needs libusb for. But on the init of libusb all those files are
    still read so a lot of apparmor denials can be seen when using usb host
    devices, like:
      apparmor="DENIED" operation="open" name="/run/udev/data/+usb:2-1.2:1.0"
      comm="qemu-system-x86" requested_mask="r" denied_mask="r"
    
    Today we could silence the warnings with a deny rule without breaking
    current use cases. But since the data in there is only a subset of those
    it can read already it is no additional information exposure. And on the
    other hand a future udev/libusb/qemu combination might need it so allow
    the access in the default apparmor profile.
    
    Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>