playbooks: roles: bifrost-create-vm-nodes: Reboot VM if boot fails

This is another attempt to solve boot problems similar to the following
ones:

net0: 52:54:00:4a:4e:de using rtl8139 on PCI00:03.0 (open)
  [Link:up, TX:0 TXE:0 RX:0 RXE:0]
  Configuring (net0 52:54:00:4a:4e:de)................ Error 0x040ee119
  (http://ipxe.org/040ee119)
  No more network devices
  No bootable device.

If boot fails (according to the BIOS' perception) then we reboot the VM.
This will assist in proceeding with normal boot in case of spurious iPXE
or DHCP problems.

Change-Id: Ibf5ec1a5d858f6e3cd510daefaf999313f4e03fc

playbooks/roles/bifrost-create-vm-nodes/files/create_vm_nodes-for-role.sh

@@ -165,7 +165,7 @@ function create_node {
     <type arch='${ARCH}' machine='${VM_MACHINE}'>hvm</type>
     <boot dev='network'/>
     <bootmenu enable='no'/>
-    <bios useserial='yes'/>
+    <bios useserial='yes' rebootTimeout='10000'/>
   </os>
   <features>
     <acpi/>