[abacus20] add network description

input/grid5000/sites/rennes/networks/swdc-a035-01-rba.yaml

@@ -25,6 +25,8 @@ swdc-a035-01-rba:
       rate: 1000000000
       kind: node
       ports:
+        8:
+          uid: abacus20-1
         10:
           uid: roazhon4-1