When ifdown isn't executed (system didn't shut down properly),
the interfaces remain in the openvswitch's database.  For the
internal ports or devices that are available when openvswitch
service starts that's not an issue.

However, ovs-vsctl won't do anything for devices created later
(Linux vlan devices for instance) since they are already in the
database. That leaves a inconsistency behind because they will
be left out of the kernel's datapath.

The ifup/ifdown will operate only on configured interfaces, so
this patch fixes the issue by deleting the interface from the
database before attempt to configure it.

Signed-off-by: Flavio Leitner <fbl@redhat.com>
Acked-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>