[test] Clarify setup of node topology.

Since the test framework automatically sets up a connection between the nodes,
the second connect_nodes call was a no-op. Remove the redundant call & add
comments to explain the expected topology.

test/functional/p2p_disconnect_ban.py

@@ -18,8 +18,11 @@ class DisconnectBanTest(BitcoinTestFramework):
 
     def run_test(self):
         self.log.info("Connect nodes both way")
+        # By default, the test framework sets up an addnode connection from
+        # node 1 --> node0. By connecting node0 --> node 1, we're left with
+        # the two nodes being connected both ways.
+        # Topology will look like: node0 <--> node1
         self.connect_nodes(0, 1)
-        self.connect_nodes(1, 0)
 
         self.log.info("Test setban and listbanned RPCs")