ironic: turn on ipxe timout

ipxe may freeze during the boot process for various reason, e.g: TFTP/HTTP
error during the initrd download. In this case ipxe will wait, this unless
a timeout is passed with the --timeout parameter.

Since force_power_state_during_sync is False, ironic won't turn off the
node and will wait instead. At the end, the node will be dropped out of
the poll of available nodes. This, just because ipxe is frozen and the
machine stay running.

Enabling this parameter can be enough to avoid this situation.

NOTE: This Mitaka backport is slighly different because
ironic::drivers::pxe::ipxe_timeout was not exposed in Hiera.

References:
http://ipxe.org/cmd/kernel
http://lists.ipxe.org/pipermail/ipxe-devel/2014-October/003829.html
Review:
  I472dfb73044df50849c9cf72de90e59151698376
  I6782f6499a8a8a9706415b3c9b22d41a9abb2e30

Closes-bug: #1353368

Change-Id: Ic0a2437f76f30a47f677c294926829978549c7fa
(cherry picked from commit 3f17a6762d)

elements/puppet-stack-config/puppet-stack-config.pp

@@ -397,6 +397,7 @@ ironic_config {
   'inspector/enabled':            value => true;
   'pxe/http_url':                 value => 'http://$my_ip:8088';
   'pxe/http_root':                value => '/httpboot';
+  'pxe/ipxe_timeout':             value => '60';
   'conductor/clean_nodes':        value => hiera('ironic::conductor::clean_nodes');
 }
 

elements/puppet-stack-config/puppet-stack-config.yaml.template

@@ -397,6 +397,7 @@ ironic::inspector::dnsmasq_interface: {{INSPECTION_INTERFACE}}
 ironic::inspector::ramdisk_collectors: {{INSPECTION_COLLECTORS}}
 ironic::inspector::additional_processing_hooks: 'extra_hardware'
 ironic::inspector::ramdisk_kernel_args: {{INSPECTION_KERNEL_ARGS}}
+ironic::inspector::ipxe_timeout: 60
 
 # Rabbit
 rabbit_cookie: {{UNDERCLOUD_RABBIT_COOKIE}}