Buffer::lookupTransform hangs with sim time clock

Bug report

Required Info:

• Operating System:
  • Ubuntu 20.04
• Installation type:
  • binaries
• Version or commit hash:
  • foxy

Steps to reproduce issue

Start gazebo and provide parameter use_sim_time value true. Create tf2_ros::Buffer with my_node->get_clock().
Then lookupTransform hangs because of time check implementation in canTransform (https://github.com/ros2/geometry2/blob/ros2/tf2_ros/src/buffer.cpp#L183).

There is better example in https://answers.ros.org/question/307682/how-to-set-up-tfbuffer-clock-in-ros-2-so-it-works-with-sim-time/

Additional information

1. lookupTransform does not freeze with zero timeout.
2. I am not sure that provided behaviour is an issue. In my projects I construct Buffer with system clocks. So it is not a problem for me now. But there are projects that use rclcpp::Node::get_clock (e.g. https://github.com/introlab/rtabmap_ros/blob/ros2/src/CoreWrapper.cpp#L132). Such projects hang with gazebo. And may be it is their problem. However, imo, if there are problems in several projects, it is better to solve it here. At least giving some words in constructor comments other than * \param clock A clock to use for time and sleeping.
3. Learning sources of Buffer I found that in lookupTransform method canTransform is called but its return value is not used (https://github.com/ros2/geometry2/blob/ros2/tf2_ros/src/buffer.cpp#L101). Is it correct?