Disabled auto screen lock and login screen after 15 min

I want to run a python script to display media content 24*7.i have disabled the screen saver, screen blanking and made the power management settings to never. And also installed light-locker. If I enter the command “xset q” to check DPMS settings it shows standby =0, suspend=0, off=0, and also DPMS is disabled ,screensaver =no.
also configured autostart file with “xset s off” , “xset s noblank”, “xset -dpms”.
I am using raspberry pi 2 model B, ubuntu-mate 16.04.
Nothing seems to work for me. After 15 minutes screen is Locked (asking password to Login). I want to avoid this login screen.