Ticket 48617 - Server ram checks work in isolation
    
    Bug Description:  Previously we would check all server cache allocations in
    isolation. We would only know if I single cache would exceed our system ram.
    This meant if you had many backends, it was possible to configure them each with
    75% of the system ram, but be a valid configuration, even though it increased
    the risk of oom.
    
    Fix Description:  Now, all backends are check in isolation *and* they are check
    as a whole regardless of manual or auto tuning. This also improves the auto
    tuning system to check it's request, and to LOWER it if it is in excess of the
    system ram. IE auto tuning a server should not ever be possible to create an OOM
    condition.
    
    https://fedorahosted.org/389/ticket/48617
    
    Author: wibrown
    
    Review by: nhosoi (Thanks!)