grub_conf.template is not OK for arm server

[Fedor Tarasenko]

I have HPE RL300 Gen11 Server with ARM processor that is capable for virtual media boot.

Problem:
During boot via redfish-virtual-media interface grub throws next error:
Can't find command linuxefi and initrdefi while booting from uefi

Workaround:
Manually edit grub menu entry and put linux/ititrd commands instead of linuxefi/initrdefi which are not available for aarch64 as noted here https://opendev.org/openstack/ironic/commit/7bb8ff3

We need option to override grub_config_template for server or detect arm bootloader during boot iso creation.