Update: The lack of entropy for the random number generator is causing this problem. As soon as I press some keys on the keyboard the system will continue to boot just fine.
The kernel prints: random: nonblocking pool is initialized when there is enough entropy for the RNG. With my two SSD systems this message is printed as soon as I hit some keys, and the system continues booting just fine. Current work arround: Added a systemd service to initialize /dev/random with enough entropy. However, the root cause is more a linux kernel issue I believe.
