Foreign threads, that are not started by jobs,
are allowed to use synchronous jobs_call/job_leave
(directly or indirectly).
This commit ensure that those foreign thread will
neither acquire the eventloop nor execute jobs.
Includes a tiny cleanup of remain usage.
Bug-AGL: SPEC-2089
Change-Id: I2ad7fcfe2c276e34bdc4ec0c2aa3a4207bea1854
Signed-off-by: José Bollo <jose.bollo@iot.bzh>