tests: refactor vpp_object.py

Move __str__ to super for all subclasses of VppObject
Implement __repr__ in VppObject
Implement __hash__ and __eq__

Change-Id: Ibd4ea37b84b17f499ab86630fb5b9ed9c8b4b1c2
Signed-off-by: Paul Vinciguerra <pvinci@vinciconsulting.com>

test/vpp_udp_encap.py

@@ -54,9 +54,6 @@ class VppUdpEncap(VppObject):
     def query_vpp_config(self):
         return find_udp_encap(self._test, self)
 
-    def __str__(self):
-        return self.object_id()
-
     def object_id(self):
         return ("udp-encap-%d" % self.id)