[CentOS] CentOS 7 1708 won't boot after grub2 update

Wed Feb 21 22:31:23 UTC 2018
Steven Tardy <sjt5atra at gmail.com>

00:1f.2 SATA controller: Intel Corporation C600/X79 series chipset 6-Port
SATA AHCI Controller (rev 06)

While I don’t have experience with this exact controller, I have seen some
LSI controllers get removed from RHEL post GA which causes similar issues.
“It worked when I installed, but after `yum update` my box doesn’t boot.”
These are typically detailed in release notes. . . We ALL read ALL release
notes? Right?