Comment # 8 on bug 908736 from grant k

The wicked upgrade, plus any/all concurrent upgrades, apparently have (at
least) increased timing of boot stages.

This apparently causes failures in device mount & local-fs service
dependencies.  Those failures wrought havoc with wicked's startup.

This fix is relevant

https://bbs.archlinux.org/viewtopic.php?pid=1180367#p1180367

and solves the problem.

Here, all !/boot partitions are on LVM-on-RAID.

Specifically creating a delaying systemd unit for required fstab mounts does
the trick.

Not clean, but works.

With that in place, switching back to 

net.ifnames=0

@ boot now completes successfully, using my net name assignments, and without
any boot issues, so far.

disabling that unit reproduces the problem.