With the PlayStation 4.50 beta still ongoing a new hidden creature has been uncovered allowing you to deactivate your primary PS4 from any secondary PlayStation 4.
Bit of a warning there is a 24-hour lock once you switch primary for that other console to become primary again. You may also want to reconsider who you gameshare now that they have the ability to deactivate your account from their system. Sony did introduce a Two-Step verification process to accessing a PlayStation Account, so you may want to consider setting that up. The guide can be found on the official PlayStation page here.
We can confirm this is indeed included in the new system software, upon trying to activate on a PS4 with 4.07 we got the following message
Our PS4 4.50 Beta