code: public static boolean removeConnectionManager(HttpClientConnectionManager connectionManager) {
          boolean wasRemoved = connectionManagers.remove(connectionManager) != null;
          if (connectionManagers.isEmpty()) {
              shutdown();
          }
          return wasRemoved;
      }
docs: Removes the given connection manager from this reaper,
  and shutting down the reaper if there is zero connection manager left.
  
  @return true if the connection manager has been successfully removed;
  false otherwise.