Forced reboot ends up NOT triggering normal unit shutdown, but only
sends TERM signal, then KILL later. Some processes such as dmeventd
do not quit on receiving TERM signal (protected), which means they
are killed after a long delay by systemd using the KILL signal.
In case the normal reboot doesn't go through, "reboot.target" will be
triggered after a timeout and send the KILL signal anyway.
Resolves: rhbz#2093133