test: ip4 vrf instances multi-context test (CSIT-492)

- add/delete IPv4 VRF instances and verify results by parsing output
  of ip_fib_dump API command and by traffic

Change-Id: I61ed5013adca29afd00b942f65be7bf964f38d85
Signed-off-by: Jan Gelety <jgelety@cisco.com>

test/vpp_interface.py

@@ -195,12 +195,16 @@ class VppInterface(object):
             self.has_ip4_config = False
         self.has_ip4_config = False
 
-    def configure_ipv4_neighbors(self):
-        """For every remote host assign neighbor's MAC to IPv4 addresses."""
+    def configure_ipv4_neighbors(self, vrf_id=0):
+        """For every remote host assign neighbor's MAC to IPv4 addresses.
+
+        :param vrf_id: The FIB table / VRF ID. (Default value = 0)
+        """
         for host in self._remote_hosts:
             macn = host.mac.replace(":", "").decode('hex')
             ipn = host.ip4n
-            self.test.vapi.ip_neighbor_add_del(self.sw_if_index, macn, ipn)
+            self.test.vapi.ip_neighbor_add_del(
+                self.sw_if_index, macn, ipn, vrf_id)
 
     def config_ip6(self):
         """Configure IPv6 address on the VPP interface."""