Refactor job to allow synchronous calls

The family of methods "jobs_invoke" make synchronous
job activation. It waits for the completion of the
job while still dispatching it internally and
providing the calling thread for processing any job
queued.

Change-Id: Id36a30789cc51245a7bbfca42f0122cf4ea623b2
Signed-off-by: José Bollo <jose.bollo@iot.bzh>