test: Use connect_nodes when connecting nodes in the test_framework

test/functional/p2p_tx_download.py

@@ -121,6 +121,7 @@ class TxDownloadTest(BitcoinTestFramework):
         #   peer, plus
         # * the first time it is re-requested from the outbound peer, plus
         # * 2 seconds to avoid races
+        assert self.nodes[1].getpeerinfo()[0]['inbound'] == False
         timeout = 2 + (MAX_GETDATA_RANDOM_DELAY + INBOUND_PEER_TX_DELAY) + (
             GETDATA_TX_INTERVAL + MAX_GETDATA_RANDOM_DELAY)
         self.log.info("Tx should be received at node 1 after {} seconds".format(timeout))