test: fix intermittent failure in rpc_setban.py --v2transport

When initiating a v2 connection and being immediately disconnected,
a node cannot know if the disconnect happens because the peer only
supports v1, or because it has banned you, so it schedules to reconnect with v1.
If the test doesn't wait for that, the reconnect can happen at a bad time,
resulting in failure in a later connect_nodes call.
Also add the test with --v2transport to the test runner.

test/functional/test_runner.py

@@ -254,6 +254,7 @@ BASE_SCRIPTS = [
     'p2p_nobloomfilter_messages.py',
     'p2p_filter.py',
     'rpc_setban.py',
+    'rpc_setban.py --v2transport',
     'p2p_blocksonly.py',
     'mining_prioritisetransaction.py',
     'p2p_invalid_locator.py',