bgp-ecmp-topo1: fix vrf default change

Python's `string' method 'replace' doesn't actually modify the string,
instead it returns a new string with the modified content.

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>

Author: rzalamena

bgp-ecmp-topo1/test_bgp_ecmp_topo1.py

@@ -139,10 +139,12 @@ def _output_summary_cmp(router, cmd, data):
         and compare with `data` contents.
         """
         output = router.vtysh_cmd(cmd, isjson=True)
-        if output.has_key('ipv4Unicast'):
-            output['ipv4Unicast']['vrfName'].replace('default', 'Default')
-        elif output.has_key('vrfName'):
-            output['vrfName'].replace('default', 'Default')
+        if 'ipv4Unicast' in output:
+            output['ipv4Unicast']['vrfName'] = \
+                    output['ipv4Unicast']['vrfName'].replace(
+                        'default', 'Default')
+        elif 'vrfName' in output:
+            output['vrfName'] = output['vrfName'].replace('default', 'Default')
         return topotest.json_cmp(output, data)
 
     test_func = functools.partial(