[rennes][abacus18] add by_path disk and eth interface type

input/grid5000/sites/rennes/clusters/abacus18/abacus18.yaml

@@ -36,12 +36,14 @@ nodes:
         mac: 70:b5:e8:de:e4:08
         ip: 172.17.109.18
       eth0:
+        interface: Ethernet
         enabled: true
         mountable: true
         mounted: true
         mac: F4:02:70:B9:60:4E
         ip: 172.16.109.18
       eth1:
+        interface: Ethernet
         enabled: false
         mountable: false
         mounted: false