Fix: Flush host interfaces in IPv6 RA integration test

EXOS sends at least one RA message even when RA is disabled before the
interface IPv6 address is configured. The IPv6 RA integration test thus
flushes the host interfaces to remove any prefixes/addresses that might
have been generated during the configuration process and test the
steady-state behavior.

Author: ipspace

tests/integration/initial/08-ra.yml

@@ -73,6 +73,11 @@ links:
 # H4: Default route, SLAAC address, prefix, DHCPv6 address (maybe)
 
 validate:
+  flush:
+    description: Flush host interfaces after initial configuration
+    nodes: [ h0, h1, h2, h3, h4 ]
+    exec:
+      frr: "ip link set eth1 down && ip link set eth1 up"
   ra:
     description: Check RA-generated default route
     wait: ra_send