Tried this exactly as you wrote but with the current stable build on a Pi3b. What happens is this: https://i.imgur.com/KJeZjIa.jpg
Here is my config:
## GPIO Controllers
## enable controllers on GPIO with mk_arcarde_joystick_rpi (0,1)
controllers.gpio.enabled=1
## mk_gpio arguments, map=1 for one controller, map=1,2 for 2 (map=1,map=1,2)
#controllers.gpio.args=map=1,2
controllers.gpio.args=map=5 gpio=5,4,14,22,13,18,21,16,6,20,26,12,-1