nodedev_list: Adjust the usb_ exclude list

The current exclude list only removes "X-X:X-X" devices; however, if
there are "X-X.X:X-X" device it doesn't find them - thus adding to the
list of expected devices, which libvirt doesn't find resulting in a
test error.

Rather than figure out all the nuances, I adjusted the "X-X" to be just
any string before a ":X-X".
Merge pull request #77 from jferlan/nodedev_list

nodedev_list: Adjust the usb_ exclude list