tests: Add stop_lttng_relayd_nocheck

Used in cases where the relay daemon might not be running.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
health check tests: test relayd and consumerd

- Cover relayd and consumerd,
- Add a test_thread_ok test (no issue found by test) to fast_regression,
- Merge duplicated code into test_health.sh.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>