Fix from Claudyus' repository

Don't show memory usage on homepage until AJAX call.

This makes the homepage load a lot faster, especially with many containers.

The tradeoff is that the memory usage doesn't show straight away, until we get a response from the AJAX call.

Also, my version of refreshMemoryContainer was broken, that is fixed now.  Was looking at data.data from the JSON response, when it was just data.