Limit non tripleo nodepool nodes to 8GB of RAM

Limit the non tripleo nodepool nodes to 8GB of RAM regardless of the
flavor used. This allows us to use arbitrary flavors that may have the
CPU resources that we require without risk that we become dependent on
the vast amounts of RAM that typically come with more CPU.

While we are at it set grub timeout to 0 saving 5 seconds of boottime
for every server we boot.

Change-Id: Ia38341239e0189c84a21a4f58dd7ca637490a27b
Merge "Limit non tripleo nodepool nodes to 8GB of RAM"