Update GRUB command line only if parameters change

The grubcmdline role can be invoked like in the following example:

    - name: Set iommu=pt
      include_role:
        name: stackhpc.linux.grubcmdline
      vars:
        kernel_cmdline:
          - iommu=pt
        kernel_cmdline_remove:
          - ^iommu=

When the role is called multiple times with parameters kernel_cmdline
and kernel_cmdline_remove, each execution moves its kernel parameters at
the end of the command line. This means each full execution would always
update GRUB, even when the end result would be the same.

Fix by comparing the existing command line with the newly generated one
as sets and only updating GRUB_CMDLINE_LINUX_DEFAULT if they are
different.

roles/grubcmdline/tasks/main.yml

@@ -53,6 +53,7 @@
     line: GRUB_CMDLINE_LINUX_DEFAULT="{{ grub_cmdline_linux_new | join(' ') }}"
     backup: "{{ backup_grub_config_file }}"
   become: true
+  when: grub_cmdline_linux_default.split() | sort | list != grub_cmdline_linux_new | sort | list
 
 - name: Generate new grub-config (RedHat <= 8.x)
   ansible.builtin.command: grub2-mkconfig