tests: restore vapi C++ test under Centos-8

The Centos-7 compiler had problems with vapi_cpp_test.cpp.
The Centos-8 compiler does not.  This change adds back the test.

==============================================================================
VAPI test
==============================================================================
run C VAPI tests                                                     1.55 OK
run C++ VAPI tests                                                   0.44 OK

==============================================================================
TEST RESULTS:
     Scheduled tests: 2
      Executed tests: 2
        Passed tests: 2
==============================================================================

Type: test

Change-Id: Ic6a655ae99eb3ba0e73b7feef4436a0ca5fd92be
Signed-off-by: Paul Vinciguerra <pvinci@vinciconsulting.com>
diff --git a/src/vpp-api/test/test_vapi.py b/src/vpp-api/test/test_vapi.py
index 1a4293d..09f9f83 100644
--- a/src/vpp-api/test/test_vapi.py
+++ b/src/vpp-api/test/test_vapi.py
@@ -4,7 +4,7 @@
 import unittest
 import os
 import signal
-from framework import VppTestCase, running_on_centos, VppTestRunner, Worker
+from framework import VppTestCase, VppTestRunner, Worker
 
 
 class VAPITestCase(VppTestCase):
@@ -47,7 +47,6 @@
                 "Timeout! Worker did not finish in %ss" % timeout)
         self.assert_equal(worker.result, 0, "Binary test return code")
 
-    @unittest.skipIf(running_on_centos, "Centos's gcc can't compile our C++")
     def test_vapi_cpp(self):
         """ run C++ VAPI tests """
         var = "TEST_BR"