Merge bitcoin/bitcoin#27128: test: fix intermittent issue in p2p_disconnect_ban

1819564 test: fix intermittent issue in `p2p_disconnect_ban` (brunoerg)

Pull request description:

  Fixes #26808

  When `node0` calls `disconnectnode` to disconnect `node1`, we should check in `node1` if it worked, because for `node0` the informations in `getpeerinfo` may be updated before really completing the disconnection.

ACKs for top commit:
  MarcoFalke:
    lgtm ACK 1819564

Tree-SHA512: 53a386fc38e2faa6f6da3536e76857ff4b6f55e2590d73fe857b3fe5d0f3ff92c5c7e4abd50ab4be250cb2106a4d14ad95d4809ea60c6e00ed3ac0e71255b0b0

Author: fanquake

test/functional/p2p_disconnect_ban.py

@@ -116,7 +116,7 @@ def run_test(self):
         self.log.info("disconnectnode: successfully disconnect node by address")
         address1 = self.nodes[0].getpeerinfo()[0]['addr']
         self.nodes[0].disconnectnode(address=address1)
-        self.wait_until(lambda: len(self.nodes[0].getpeerinfo()) == 1, timeout=10)
+        self.wait_until(lambda: len(self.nodes[1].getpeerinfo()) == 1, timeout=10)
         assert not [node for node in self.nodes[0].getpeerinfo() if node['addr'] == address1]
 
         self.log.info("disconnectnode: successfully reconnect node")
@@ -127,7 +127,7 @@ def run_test(self):
         self.log.info("disconnectnode: successfully disconnect node by node id")
         id1 = self.nodes[0].getpeerinfo()[0]['id']
         self.nodes[0].disconnectnode(nodeid=id1)
-        self.wait_until(lambda: len(self.nodes[0].getpeerinfo()) == 1, timeout=10)
+        self.wait_until(lambda: len(self.nodes[1].getpeerinfo()) == 1, timeout=10)
         assert not [node for node in self.nodes[0].getpeerinfo() if node['id'] == id1]
 
 if __name__ == '__main__':