[APPS-425] Salesforce app unable to auto-refresh (promptly) when using "next ticket" button

*JIRA: https://zendesk.atlassian.net/browse/APPS-425*

Ticket workspaces are refreshing/re-activating installed apps in a timely manner. Because a workspace is re-used when 'next-ticketing', each app view remains in it's existing state after workspace refresh until it redraws itself in response to an AJAX request (or some other mechanism internal to that app).

What this means is that we should build our own apps in a way that they will handle this scenario and update their visual state accordingly.

This PR updates the Salesforce app so that it will redraw to loading state promptly when a ticket is replaced.

/cc @jwswj @s-vizzari