UI: system memory usage is including buffer/cache again

Problem

In the server listing in the UI the memory usage bar is including the memory used by the operating system for buffers/cache. As a result this make it look like the system is using more memory than expected. The state also becomes pointless because in most long running system the kernel will try to fill spare memory with buffer and cache data to speed p the system.

I believe this a regression (MB-4786), as previously we report the system memory usage not including the buffers and caches.