Version 2 transactions remain non-standard until CSV activates

Before activation, such transactions might not be mined, so don't
allow into the mempool.

- Tests: move get_bip9_status to util.py

- Test relay of version 2 transactions

Github-Pull: #7835
Rebased-From: e4ba9f6b04 5cb1d8a207 da5fdbb3a2

qa/rpc-tests/test_framework/util.py

@@ -490,3 +490,10 @@ def create_lots_of_big_transactions(node, txouts, utxos, fee):
         txid = node.sendrawtransaction(signresult["hex"], True)
         txids.append(txid)
     return txids
+
+def get_bip9_status(node, key):
+    info = node.getblockchaininfo()
+    for row in info['bip9_softforks']:
+        if row['id'] == key:
+            return row
+    raise IndexError ('key:"%s" not found' % key)