set up pxe server in uefi mode

1. uefi is using the EFI/BOOT/BOOTX64.efi, the configure file will be BOOTX64.conf  , (but we should change it to efidefault, also if you know the  client ip, you can also change the efidefault file to 'gethostip -x $ip'.

2. the boot parameter in elidefault should be like the follows :

title  5Boot ovirt-node-image
  root (nd) # this is important.
  kernel /EFI/BOOT/vmlinuz0 root=live:/ovirt-node-image-mcp-7.3.iso rootfstype=auto ro liveimg nomodeset check rootflags=loop crashkernel=512M-2G:64M,2G-:128M elevator=deadline processor.max_cstate=1 install rhgb rd_NO_LUKS rd_NO_MD rd_NO_DM
  initrd /EFI/BOOT/initrd0.img