Auto-configure swap

Create a swapfile and configure it to be used for swap, immediately and
on boot; defaults to half the size of RAM. See attribute for overriding
configs to tune size or swappiness.

site-cookbooks/kosmos_kvm/attributes/default.rb

@@ -11,3 +11,10 @@ node.default["kosmos_kvm"]["host"]["qemu_base_image"] = {
 node.default["kosmos_kvm"]["backup"]["schedule"] = "0/3:00"
 # Node/VM names excluded from backups
 node.default["kosmos_kvm"]["backup"]["nodes_excluded"] = []
+
+node.default["kosmos_kvm"]["guest"]["swap"] = {
+  "enabled" => true,    # set to false to disable swap on a guest
+  "size_mb" => nil,     # nil => auto (half of RAM); integer => fixed MB; 0 => disabled
+  "path" => "/swapfile",
+  "swappiness" => nil   # nil => leave kernel default; e.g. 10 to tune
+}