[test] wait for disconnect before asserting len(peerinfo)

-Need to wait for disconnect to complete because number
of connected peers is tested later

test/functional/feature_maxuploadtarget.py

@@ -135,7 +135,7 @@ def run_test(self):
 
         self.log.info("Peer 2 able to download old block")
 
-        self.nodes[0].disconnect_p2ps()
+        self.nodes[0].disconnect_p2ps(wait_for_disconnect=True)
 
         self.log.info("Restarting node 0 with noban permission and 1MB maxuploadtarget")
         self.restart_node(0, ["[email protected]", "-maxuploadtarget=1"])