Fix: leak of lttng-consumerd global HTs in run-as worker

All resources allocated by the consumerd before the launch
of the run-as worker process are leaked since the run-as process
is only fork()'ed (the original process image is preserved).

Moving the launch of the worker earlier in the initialization
of the consumerd works around this problem.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>