it seems that relevant OVS patches still did not land [1][2].
I think we should revert and wait for the patches to merge first,
then we can go ahead and merge in os-vif with release note that states
the exact OVS version required.
[1] https://patchwork.ozlabs.org/patch/1186896/
[2] https://patchwork.ozlabs.org/patch/1215075/
This reverts commit 399e355088.
Change-Id: I7cd6112b3b35a6971d3d354abae7652344ed1c97