ctdb-eventscripts: Remove special case for virtio_net

ctdb-eventscripts: Remove special case for virtio_net

The current check is incorrect in 2 ways:

* Commit be71a84565e9e7532a77c175732b764d1f42c1cd contained a thinko
  that stops virtio_net interfaces from simply being marked up

* virtio_net interfaces can actually be down

virtio_net has supported ethtool since Linux 2.6.29, so just remove
the special case.  This means that testing CTDB on very old virtual
machines is not supported.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
Autobuild-User(master): Amitay Isaacs <amitay@samba.org>
Autobuild-Date(master): Thu Jul 31 13:08:47 CEST 2014 on sn-devel-104