make sure boardd loopback test can run standalone

selfdrive/boardd/tests/test_boardd_loopback.py

@@ -30,11 +30,10 @@ def reset_panda(fn):
 os.environ['STARTED'] = '1'
 os.environ['BOARDD_LOOPBACK'] = '1'
 os.environ['PARAMS_PATH'] = PARAMS
+
 @reset_panda
 @with_processes(['boardd'])
 def test_boardd_loopback():
-
-
   # wait for boardd to init
   spinner = Spinner()
   time.sleep(2)
@@ -81,3 +80,7 @@ def test_boardd_loopback():
       assert not len(sent_msgs[bus]), f"loop {i}: bus {bus} missing {len(sent_msgs[bus])} messages"
 
   spinner.close()
+
+
+if __name__ == "__main__":
+    test_boardd_loopback()