I get this "[FAILED] Failed start Load Kernel Modules. See 'systemctl status systemd-modules-load.service' for details." on boot. I only got one module loaded on boot, that is nf_nat_ftp. And it loads alrite, but that message on boot doesn't feel right. However i can get rid of that message. If /etc/modules-load.d directory is empty while installing a [new] kernel, then no message appears on booting that kernel, even if i load modules by moving nf_nat_ftp.conf back to /etc/modules-load.d directory before reboot. Seems like install script looks for the contents of that directory while installing a kernel and does something wrong.
It's easy to reproduce:
# echo 'nf_nat_ftp' > /etc/modules-load.d/nf_nat_ftp.conf
Then just install a kernel, either the new one, or a previous one. Then reboot and boot the newly installed kernel.
# yum install 3.10.0-957.21.2.el7
# shutdown -r now
You don't even need the module (and it's dependencies, if any) to be loaded while installing the kernel. So i ain't sure if this is a bug of systemd, kernel install script or systemd-modules-load.service file, but it bothers to move contents of /etc/modules-load.d directory to some other place everytime before installing a new kernel if you wanna clean boot, without any error messages.