Removing test of random xid from header class.

The responsibility of randomizing XIDs was delegated to GenericMessage
class.

Author: diraol

tests/v0x01/test_common/test_header.py

@@ -44,9 +44,3 @@ def test_unpack(self):
         self.assertEqual(self.message.version, 1)
 
         f.close()
-
-    @patch('pyof.v0x01.common.header.randint')
-    def test_random_xid(self, m):
-        """Each Header instantiations without xid should call randint."""
-        Header(), Header()  # noqa
-        self.assertEqual(m.call_count, 2)