Persona ExtJS store breaks when CMS and site are running on different hosts

The persona store in ExtJS does not work when CMS and site are running on different hosts, because the persona store REST call does not ignore the rendering host stored in the HTTP session by the HST.
As a result, once the rendering host is stored in the HTTP session, the persona store does not work anymore.

Steps to reproduce:
1. move the CMS REST mount to a different host in the HST host configuration
2. select a channel in the channel manager perspective and click 'Open Channel'
3. open the persona manager by clicking on the marketing perspective icon.

Expected behavior: the list of personas is shown
Actual behavior: a 404 error is reported