Fixes #38178 - Add linuxefi/initrdefi wrapper to GRUB2 templates

Back in time, GRUB2 is using `linux` and `initrd` commands to load the
kernel and initrd into ram on legacy BIOS. Later, `linuxefi` and
`initrdefi` commands have been added to do the same on UEFI platforms.

However, it looks like that `linuxefi` and `initrd` commands are
deprecated and distributions like Ubuntu started to remove them starting
with 24.04.

In case of Secure Boot [1] and Ubuntu 24.04 - putting corresponding
shim+GRUB2 binaries in bootloader universe directory - the network boot
is not working anymore because of used `linuxefi/initrd` commands in the
involved GRUB2 configuration templates.

In order fix this we can simply add wrapper functions to provide
`linuxefi`/`initrdefi` as commands.

[1]:theforeman#9864

app/views/unattended/provisioning_templates/PXEGrub2/preseed_default_pxegrub2.erb

@@ -15,16 +15,14 @@ description: |
 #
 # This file was deployed via '<%= template_name %>' template
 
-<%
-  os_major = @host.operatingsystem.major.to_i
-  os_name  = @host.operatingsystem.name
+# Wrapper for deprecated linuxefi/initrd commands
+function linuxefi {
+  linux $*
+}
+function initrdefi {
+  initrd $*
+}
 
-  if (os_name == 'Ubuntu' && os_major > 12) || (os_name == 'Debian' && os_major > 8)
-    efi_suffix = 'efi'
-  else
-    efi_suffix = ''
-  end
--%>
 set default=0
 set timeout=<%= host_param('loader_timeout') || 10 %>
 

app/views/unattended/provisioning_templates/PXEGrub2/preseed_default_pxegrub2_autoinstall.erb

@@ -18,16 +18,21 @@ test_on:
 # lang = en_US
 #   System locale
 #
-<%
-  efi_suffix = 'efi'
--%>
+
+# Wrapper for deprecated linuxefi/initrd commands
+function linuxefi {
+  linux $*
+}
+function initrdefi {
+  initrd $*
+}
 
 set default=0
 set timeout=<%= host_param('loader_timeout') || 10 %>
 
 menuentry '<%= template_name %>' {
-  linux<%= efi_suffix %> <%= @kernel %> root=/dev/rd/0 rw auto <%= snippet('preseed_kernel_options_autoinstall', variables: {add_userdata_quotes: true}).strip %>
-  initrd<%= efi_suffix %> <%= @initrd %>
+  linuxefi <%= @kernel %> root=/dev/rd/0 rw auto <%= snippet('preseed_kernel_options_autoinstall', variables: {add_userdata_quotes: true}).strip %>
+  initrdefi <%= @initrd %>
 }
 
 <%= snippet_if_exists(template_name + " custom menu") %>

app/views/unattended/provisioning_templates/PXEGrub2/pxegrub2_global_default.erb

@@ -7,6 +7,14 @@ description: |
   The output is deployed on the host's subnet TFTP proxy.
   Do not associate or change the name.
 -%>
+# Wrapper for deprecated linuxefi/initrd commands
+function linuxefi {
+  linux $*
+}
+function initrdefi {
+  initrd $*
+}
+
 default=<%= global_setting("default_pxe_item_global", "local") %>
 timeout=20
 echo Default PXE global template entry is set to '<%= global_setting("default_pxe_item_global", "local") %>'