fuel-plugin-ovs: FIXME: Pin to pre-Newton upstream

fuel-plugin-ovs: FIXME: Pin to pre-Newton upstream

Upstream Fuel@OPNFV made the switch to Newton, while in Armband
this will happen later.

Until then, pin the latest Mitaka compatible version, i.e. use
the Fuel@OPNFV reference from the Colorado branch.

While at it, add missing change var for upstream fuel-plugin-ovs
git repo, to prevent issues like ARMBAND-166 from happening on
Armband master later.

JIRA: ARMBAND-166
JIRA: ARMBAND-118

Change-Id: I0630c2349befa3bdfbbb01b4ad401660d8cfd5fe
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>