af-binder: Fix of subscribe issue
Enforce serialization of messages, makes event really asynchronous,
and enforce (un)subscribe in living request.
Include the following changes:
*
9194450 afb-evt: send events in separate job
*
034b0ab Revert "afb-stub-ws: Allow unordered process of messages"
*
328c4b5 (guppy-next) afb-xreq: Forbids (un)subscribes after reply
Bug-AGL: SPEC-2215
Bug-AGL: SPEC-2219
Bug-AGL: SPEC-2542
Bug-AGL: SPEC-2599
Change-Id: I84b2d1c46c13c1f18c2eb466284d2b4fc8fedc0b
Signed-off-by: José Bollo <jose.bollo@iot.bzh>