ENYO-2291: remove old express-2.x code

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>
ENYO-2291: do not re-assign the context of common-us callbacks

- clarify return clauses
- do not call `bind()` on `next()`

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>