establish the "standard" virtual machine / instance size in Ganeti

Ganeti clusters can define parameters for minimum, maximum and "standard" instance sizes. This is currently:

# gnt-cluster info
[...]
Instance policy - limits for instances: 
  bounds specs: 
    - max/0: 
        cpu-count: 8
        disk-count: 16
        disk-size: 1048576
        memory-size: 32768
        nic-count: 8
        spindle-use: 12
      min/0: 
        cpu-count: 1
        disk-count: 1
        disk-size: 1024
        memory-size: 128
        nic-count: 1
        spindle-use: 1
  std: 
    cpu-count: 1
    disk-count: 1
    disk-size: 1024
    memory-size: 128
    nic-count: 1
    spindle-use: 1
  allowed disk templates: drbd, plain
  vcpu-ratio: 4
  spindle-ratio: 32
[...]

We should at least define some sort of "standard" here and define what the minimum and maximums should be.

for what it's worth, the average memory size right now is around 5GB

root@fsn-node-01:~# echo \($(gnt-instance list | awk '{ print $NF }' | grep G'$' | sed 's/G$/+/')0\) / $(gnt-instance list | awk '{ print $NF }' | grep G'$' | wc -l) | bc -l 
4.80769230769230769230

more investigation would be required to evaluate standard disk and CPU sizes.