🐞 Issue Title: usbipd attach fails with "Unable to determine host address" in NAT mode (WSL 2)

[woque]

Describe the bug
When trying to attach a USB device to WSL 2 using usbipd attach --wsl --busid 3-4, the command fails with the following error:

usbipd: info: Using WSL distribution 'Ubuntu-20.04' to attach; the device will be available in all WSL 2 distributions.
usbipd: info: Detected networking mode 'nat'.
usbipd: error: Unable to determine host address.

[dorssel]

You can workaround this by manually specifying --host-ip.

Question is still: why does the auto-detect not work?

What is the output of (from PowerShell):

wsl --distribution Ubuntu-20.04 --user root --cd / --exec /bin/cat /proc/net/route