The only reason we need newer openvswitch is following fix [1] for
user-space part of openvswitch. This patch fixes our
test_install_flood_to_tun tests.
Current 2.6 branch has issues with ovsdb where connection with native
interface is getting lost and functional job gets stuck. To mitigate
that, this patch switches back to OVS 2.5.1 version for functional jobs,
compiling only user-space part as OVS 2.5.1 kernel modules are not
supported by Xenial.
Fullstack job remains running with 2.6 because the job needs OVS kernel patch
for local VXLAN tunneling.
[1] 56de2148f6
Related-bug: bug/1646107
Change-Id: Ic5419afe7170e759749afd7055441c82c317efe0
b0ea7c95a3