Hello,
I have the exact problem that you have. Upon upgrading to OS X ver. 10.11.5, my mid 2014 15" MBPr is unable to shutdown, log off, or restart. Everytime I perform these actions, the menu bar for the finder disappears, but I still have my dock and I am still able to run apps.
The following are the solutions I have tried so far and worked:
If you decide to keep the update, then you can try performing the said actions through terminal since you are still able to open and run apps in that moment.
shutdown: in terminal, type "sudo halt" (without ") then type your password, then press enter.
restart: in terminal, type "sudo reboot" (without ") then type your password, then press enter.
Or you can also do a Time Machine restore to version 10.11.4 if you have one.
For me, I decided to restore my mac to version 10.11.4 and will probably hold on to updating to 10.11.5 until it gets fixed.
Hope this helps,
JR