tests: fix TEST= filtering for python3

Type: fix

Change-Id: Iceb60e8a507120434cfc68758476ff5351b05f58
Signed-off-by: Klement Sekera <ksekera@cisco.com>
diff --git a/test/run_tests.py b/test/run_tests.py
index b6c178f..a34cf48 100644
--- a/test/run_tests.py
+++ b/test/run_tests.py
@@ -822,7 +822,7 @@
         # don't fork if requiring interactive terminal
         print('Running tests in foreground in the current process')
         full_suite = unittest.TestSuite()
-        map(full_suite.addTests, suites)
+        full_suite.addTests(suites)
         result = VppTestRunner(verbosity=verbose,
                                failfast=failfast,
                                print_summary=True).run(full_suite)