In order to support {CentOS,RHEL}7 for building cloud images we need to
handle the differences in grub packaging from Ubuntu. We also need to
populate the defualt location for cloud images for CentOS builds.
Change-Id: Ie0d82ff21a42b08c4cb94b7a5635f80bfabf684e
bootloader
Installs grub[2] on boot partition on the system. In
case GRUB2 is not available in the system, a fallback to Extlinux will
happen. It's also possible to enforce the use of Extlinux by exporting a
DIB_EXTLINUX variable to the environment.
Arguments
DIB_GRUB_TIMEOUTsets thegrubmenu timeout. It defaults to 5 seconds. Set this to 0 (no timeout) for fast boot times.DIB_BOOTLOADER_DEFAULT_CMDLINEsets the CMDLINE parameters that are appended to the grub.cfg configuration. It defaults to 'nofb nomodeset vga=normal'