Fix backup VM name for ldap-3

(and potentially other guests where the name differs from the libvirt
domain name)

site-cookbooks/kosmos_kvm/recipes/backup.rb

@@ -38,7 +38,7 @@ cookbook_file "/root/backups/backup_vm.sh" do
 end
 
 # Search all guests and filter by presence on current host
-vm_domains = search(:node, "role:kvm_guest").map(&:name) \
+vm_domains = search(:node, "role:kvm_guest").map{|n| n["hostname"] } \
              & `virsh list --name`.strip.chomp.split("\n")
 
 template "/root/backups/backup_all_vms.sh" do