message: [network] Fix flaky test in connectivity_manager
  This diff removes an unnecessary upper bound on linear backoff in
  connectivity_manager test. The upperbound was randomly chosen and in
  reality makes the test flaky. It also does not add much value.
  Closes:
  Approved by: bmwill
diff: @@ -662,7 +662,6 @@ fn backoff_on_failure() {
  let elapsed = Instant::now().duration_since(start);
  info!("Duration elapsed: {:?}", elapsed);
  assert!(elapsed.as_millis() >= 100);
  - assert!(elapsed.as_millis() <= 150);
  }
  };
  rt.block_on(events_f.boxed().unit_error().compat()).unwrap();
  