Changing the IP table for an interface is an error if the interface already has an address configured (VPP-601)

Change-Id: I311fc264f73dd3b2b3ce9d7d1c33cd0515b36c4a
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/test/test_ip4_vrf_multi_instance.py b/test/test_ip4_vrf_multi_instance.py
index ddf8f59..b73ac94 100644
--- a/test/test_ip4_vrf_multi_instance.py
+++ b/test/test_ip4_vrf_multi_instance.py
@@ -208,6 +208,7 @@
             self.vrf_deleted_list.append(vrf_id)
         for j in range(self.pg_ifs_per_vrf):
             pg_if = self.pg_if_by_vrf_id[vrf_id][j]
+            pg_if.unconfig_ip4()
             if pg_if in self.pg_in_vrf:
                 self.pg_in_vrf.remove(pg_if)
             if pg_if not in self.pg_not_in_vrf: