tempest.scenario.test_network_basic_ops.TestNetworkBasicOps.test_mtu_sized_frames fails constantly

Hi,
Due to the csit change that was merged yesterday, that added provider vlan testing, tempest.scenario.test_network_basic_ops.TestNetworkBasicOps.test_mtu_sized_frames started failing all the time.
This because of incompatibility between the mtu of the ping request tempest sends, and the mtu of tempest external network that was changed because it is now a vlan network.

We will skip this test across versions, and try to come up with a fix ASAP.

https://jenkins.opendaylight.org/releng/view/netvirt-csit/job/netvirt-csit-1node-openstack-newton-nodl-v2-upstream-learn-carbon/176/