USB panic

[Phil Nelson <phil%NetBSD.org@localhost>]

Hello, 

   I'm running NetBSD 8.99.19 (GENERIC) #0: Sun Jun 17 15:06:27 UTC 2018
on a DELL Optiplex 3020 with a KVM with keyboard/mouse over USB.   Switching
machines detaches the USB from one machine and re-attaches it to the other.

   I just got the following panic today when switching to the 3020:

reboot after panic: [ 6152.6922077] panic: kernel diagnostic assertion "xfer->ux_state == XFER_ONQU" failed: file "/usr/src/sys/dev/usb/usbdi.c", line 914 

Is this a known problem?  I'm not finding a PR with xu_state in the PR.

--Phil