Collapse the override interface.vpp files

These interfaces follow a clear pattery of daisychaining and can be
computed using {{node.id}} and {{lab.id}}.

TESTED: Generating a new output has only expected diffs in the comments,
not in any IP or MTU or state values.

build/default/hvn1.lab.ipng.ch/vpp1-3/etc/vpp/config/interface.vpp

@@ -1,4 +1,4 @@
-comment { Gi10/0/0 is connected to vpp1-2:Gi0/0/1 }
+comment { Gi10/0/0 is connected to vpp1-2:Gi10/0/1 }
 set interface mtu 9000 GigabitEthernet10/0/0 
 set interface mtu packet 9000 GigabitEthernet10/0/0
 set interface ip address GigabitEthernet10/0/0 2001:678:d78:211::3:13/112