As OVS treats ff:ff:ff:ff:ff:ff as no mask, when OpenFlowPlugin gets
statistics from OVS it do not receive any mask and then comparison
checks in CSIT tests are failing due to this, but it is correct
behaviour.
Change-Id: I7ec105047d1b80090b13caba4c93cc1df6af5d0d Signed-off-by: Tomas Slusny <tomas.slusny@pantheon.tech>