Register XHR request callback gets interrupted by Google Chrome

[wstrm]

With a cold browser cache the XHR request callback gets interrupted by Google Chrome. This is probably due to the 6 max TCP connections limit in the web browser. This bug only occurs for Google Chrome with a cold cache, if the cache is warm there is no issues.

The interrupt will stop Mithril.js from redirecting to the front page upon a succesful registration. The user registration is correctly registered by the backend and the user is still able to login with the newly created account.