Improve safety of link to event loop

Instead of using the default one that depends on the
current thread and that might be shared with other
items, use an explicit new one running in a dedicated
thread.

Bug-AGL: SPEC-2130

Change-Id: Ie609d19157a5dcaf6e5fa3896dc91d88ba5f214a
Signed-off-by: José Bollo <jose.bollo@iot.bzh>