setup_node.sh turns off system swapping

[EricAllman]

The setup_node.sh script turns off virtual memory swapping (using swapoff -a) and never turns it back on again. I assume this has something to do with making sure that $SECRET doesn't leak any information, but it does leave the system in a potentially different state after running the script.

[m-hemmings]

This is actually not a bug, exactly. As per this issue:
kubernetes/kubernetes#53533
Swap is not supported on worker nodes. I am monitoring that for a fix if it's implemented, but for how this is the reason swap is disabled.