xen scripts' eth0 assumption broken by biosdevname

[Saul St. John]

There are a number of scripts in /etc/xen/scripts (e.g. vif-bridge, vif-nat, &c) that use 'eth0' as a default interface when one isn't provided.

That's good and useful when it's the correct choice-- and for me, prior to Quantal, it was. But then biosdevname came along and renamed my PowerEdge servers' nics "em1" and "em2", violating these scripts' implicit assumptions about interface names.

Since the biosdevname behavior isn't going to change (I gather?), these scripts should be fixed to make a more reasonable assumption on systems like mine.