Add in a concurrent test to test_logging_output_format.py (#209)
Add in a concurrent test to test_logging_output_format.py (#209)

* Add in a concurrent test to test_logging_output_format.py

Before this PR, there was only a post_shutdown_test.  Due
to a bug in launch_testing, having only a post_shutdown test
causes stack traces to be printed while starting up the tests.
Add in this workaround to quiet the problem until the bug
is fixed.

Signed-off-by: Chris Lalancette <281cd07d7578d97c83271fbbf2faddb83ab3791c@openrobotics.org>
ros2/c_utilities,ros2/c_utilities