LP#1716479: (follow-up) fix handling of onSave callbacks for AngularJS MARC edit

LP#1716479: (follow-up) fix handling of onSave callbacks for AngularJS MARC edit

This patch fixes an issue that has been present for a while but
clarified by Beth Wills in the course of testing the base patch
for this bug.

Specifically, the routine to process onSave callbacks was
not bound to the scope properly, meaning that the wrong onSave
callbacks could be run when dealing with mutiple active
egMarcEditRecords.

Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>