Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1254909
Description of problem:
When you click on show diff on the history page of a provisioning template (which has a history), it opens duplicate tabs in the browser.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. Create custom prov template and submit
2. Change template and submit
3. Click on show diff on the history tab of template

Actual results:

Expected results:

Additional info:
Tested with Firefox 39.0.3 on Fedora and Firefox 40 on Windows.