Auto boot is one of the new features of both the 13inch and 15inch Macbook Pro (late 2016). When you either attach a power source or open the lid (barring there is enough battery power) the device will startup.
To disable this feature open the Terminal.app and type in:
sudo nvram AutoBoot=%00
- exatcly as it is shown here.
To enable this feature open the Terminal.app and type in:
sudo nvram AutoBoot=%03