[APPS-272] Fix inconsistency when linking to an existing jira issue

The 'change' event is not firing when saving the ticket immediately after typing the story ID. This is a temporary workaround until apps have access to the 'ticket.save' event.

JIRA issue: https://zendesk.atlassian.net/browse/APPS-272

/cc @jakeisonline @jamesarosen @jwswj