Fixed port chain direction and linking

Given a port chain of two port pair groups ppg1 and ppg2, which each
consist of a single port pair (ppg1=[pp1], ppg2=[pp2]), where
pp1=(ingress: p1, egress: p2), p2=(ingress: p3, egress: p4) the
following forwarding chain was generated:

    /----\ /----\
    | s1 | | s2 |
    \i--e/ \i--e/
     v  ^   v  ^
     |  |   |  |
     \--/   \--/

This, for once, mixed ingress and egress, but also did not actually link
the servers.

This patch corrects the linking to:

    /----\ /----\
    | s1 | | s2 |
    \i--e/ \i--e/
     ^  v   ^  v
     |  |   |  |
    -/  \---/  \->

Change-Id: Iabc48a6950f864562a93f8d17f41890598d65ac6
Signed-off-by: schillinge <ablu@mail.uni-paderborn.de>