ProxyDAO.listen:  Fix bug where predicate is not being applied to listener.
ProxyDAO.listen:  Fix bug where predicate is not being applied to
listener.

Instead of calling delegate.listen_ we call this.listen_ so things
like FilteredDAO can still decorate the listener.

jacksonic/vjlofvhjfgm,foam-framework/foam2,foam-framework/foam2,jacksonic/vjlofvhjfgm,jacksonic/vjlofvhjfgm,foam-framework/foam2,foam-framework/foam2,foam-framework/foam2