xennet: rx no mbuf

[Sarton O'Brien <bsd-xen%roguewrt.org@localhost>]

I'm seeing the error:

        xennet: rx no mbuf

Quite a bit lately. Only seems to happen when building without redirecting 
stdout.

Once it occurs, the system is unusable. I haven't attempted to drop to ddb 
yet.

kernel and userland no more than a day old.

This is an amd64 domu.

Sarton