Ignore IPP-over-USB devices if ipp-usb claims them

[zdohnal]

This is basically a clone of CUPS issue, which is applicable to printer application written by PAPPL as well.

The core idea:

• find the device on USB
• check whether the same device is not advertised on mDNS already - which means ipp-usb is running and advertises it
• if the device is advertised, ignore it in PAPPL's USB backend