Fix: add missing JUL loglevel handling

JUL loglevels are directly mapped to the Level class from the JUL
interface. A complete listing has been added to the enable-event help
command and to the lttng.h ABI as lttng_loglevel_jul.

Signed-off-by: David Goulet <dgoulet@efficios.com>
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>