Mac book pro Sierra does not shutdown - stays idle with a black screen and mouse pointer
The solution I have found  after long suffering this problem in High Sierra after trying to upgrade from version 10.13.5 to 10.13.6. I deleted these files through terminal, then rebooted. 

You may need to run with admin permissions, i.e. "sudo rm -f etc." and enter your admin password when asked:

rm -f /Library/Preferences/com.apple.loginwindow.plist

rm -f /private/var/db/.AppleUpgrade

rm -f /private/var/db/.SoftwareUpdateAtLogout

reboot