Comment 5 for bug 1533876

@markus_z

if you have a ubuntu 14.04 system and run the following command it will result in an
exit code of 1

stack@silpixa00390506:~/devstack$ ip link set eth50 mtu 1000
Cannot find device "eth50"
stack@silpixa00390506:~/devstack$ echo $?
1

as the vhost-user ports are not represented in the kernel network stack setting the
mtu on vhost-user port will always cause the binding to be failed with any version of
ip link /iproute2 package that returns 1 when a device is not found.

to replicate the nova boot issue you would need to deploy ovs with dpdk though that is not nessacary
as the root cause is the uncaught return code caused by the incorrect call to set the mtu.

the patch i have submitted will remove the errant call to ip link to set the mtu.
it also make the creation of the vhost-user port atomic which will silence an ovs error message that is currently emitted
every time a vhost-user port is created due to the type not being set as part of the create.

ideally this change should be backported to kilo and liberty as the non atomic create and mtu issue have always been present since support was introduced in kilo.