fix an exception raised while press ctrl+c to exit

[iuhilnehc-ynos]

to fix part of https://github.com/osrf/ros2_test_cases/discussions/1048 rclpy._rclpy_pybind11.RCLError: failed to shutdown: rcl_shutdown already called on the given context, at ./src/rcl/init.c:313

[iuhilnehc-ynos]

It seems like a workaround.

The other part about unload warning can be fixed with https://github.com/ros-visualization/qt_gui_core/pull/274

I'd like to share the fixed method even if it's not good.

[clalancette]

CI:

• Linux
• Linux-aarch64
• Windows

[Yadunund]

@mergifyio backport iron

[mergify[bot]]

backport iron

✅ Backports have been created

* [#292 fix an exception raised while press ctrl+c to exit (backport #291)](https://github.com/ros-visualization/rqt/pull/292) has been created for branch `iron`