Issue #1623114 by ParisLiakos, chrisdolby, marvil07: Remove drupal_exit().

core/includes/ajax.inc

core/includes/common.inc

core/includes/install.inc

core/modules/image/image.module

core/modules/locale/locale.bulk.inc

.../lib/Drupal/overlay/EventSubscriber/OverlaySubscriber.php

core/modules/overlay/overlay.module

core/modules/system/tests/modules/form_test/form_test.module

core/modules/xmlrpc/xmlrpc.server.inc