Tests: Add health check testpoint fail test

Tests: Add health check testpoint fail test

This test trigger a failure in a specified thread by using the testpoint
mechanism. The testpoints behavior is implemented in health_fail.c. The
testpoint code simply return 1 (non-zero values are considered as errors
for testpoints) to trigger the specific thread error handling mechanism.

This test ensure that we can detect health failure for each thread error
handling paths.

Signed-off-by: Christian Babeux <christian.babeux@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>