[Backport to v2022] Use SIGTERM to terminate test-introspection

The test-introspection binary has a custom SIGINT handler that tells the user to press Ctrl-C again to quit, thus it would require a second SIGINT to actually terminate. However, getting the timing between both in order for the handler to run is racy, so as an alternative, we just send SIGTERM instead, which has no custom handler and thus quits test-introspection as expected.

https://phabricator.apertis.org/T8377

Signed-off-by: Ryan Gonzalez ryan.gonzalez@collabora.com