hotplug/Linux: update to new ip command syntax.

hotplug/Linux: update to new ip command syntax.

The current usage prevents naming a vif "dev". Although the current syntax is
documented in Squeeze's ip(8) it appears that this was a documentation bug.
Newer versions of the man page describe the new syntax used here and Squeeze's
implementation accepts it as well.

This is Debian bug #705659.
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=705659

Mike provided the initial patch to tools/hotplug/Linux/xen-network-common.sh
and Ian extended it to catch some cases in vif-* too.

Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Signed-off-by: Mike <debian@good-with-numbers.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Release-acked-by: George Dunlap <george.dunlap@eu.citrix.com>