Regression: CMS does an improper redirect to /cms when the proxy preserves the host headers

When the reverse proxy preserves the requested host headers for the CMS an improper redirect happens to /cms.

This seems to be introduced in maintenance release 2.24.17.

Steps to reproduce:

1. Create a new project with the 7.8.9 based archetype http://www.onehippo.org/7_8/trails/developer-trail/hippo-baby-steps.html
2. Build and run the project
3. Setup Apache httpd as a reverse proxy according to http://www.onehippo.org/library/deployment/configuring/configure-apache-httpd-web-server-for-cms-and-sites.html
4. Set the ProxyPreserveHost directive to On for the CMS
5. See you can login as normal
6. Stop the project
7. Bump to the latest maintenance release version for the cms by adding the property:
<hippo.cms.version>2.24.17</hippo.cms.version>
8. Run the project
9. Try to login and see an incorrect redirect to /cms