tests: return the proper TAP exit code

tests: return the proper TAP exit code

The C TAP library provides the 'exit_status()' function that will return
the proper exit code according to the number of tests that succeeded or
failed.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: Ia76ed7d1510bb23bf3848f85ac9022c66e752311
(cherry picked from commit d6641c890cd38d0c43a84fd54ccf3c10de88a56b)
Reviewed-on: https://review.lttng.org/c/babeltrace/+/12475
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
CI-Build: Simon Marchi <simon.marchi@efficios.com>
Tested-by: jenkins <jenkins@lttng.org>