tests: Add testcase for SRv6 End.DX6

Signed-off-by: Carmine Scarpitta <cscarpit@cisco.com>

tests/topotests/zebra_seg6local_route/r1/routes.json

@@ -119,5 +119,29 @@
         }]
     }],
     "required_kernel": "5.14"
+  },
+  {
+    "in": {
+      "dest": "6::1",
+      "context": "End_DX6 2001::1"
+    },
+    "out":[{
+        "prefix":"6::1/128",
+        "protocol":"sharp",
+        "selected":true,
+        "destSelected":true,
+        "distance":150,
+        "metric":0,
+        "installed":true,
+        "table":254,
+        "nexthops":[{
+            "flags":3,
+            "fib":true,
+            "active":true,
+            "directlyConnected":true,
+            "interfaceName": "dum0",
+            "seg6local": { "action": "End.DX6" }
+        }]
+    }]
   }
 ]