That feature is added after someone requested it.
Podbots are tweaked in this way so they cannot see an enemy ( or ally ) if he's in a dark area ( doesn't necessary has to be pitch black I guess ), but only if there is no sound or any other factor that will blab his position.
So the bots are programmed to use a flashlight in dark area's to increase the chance of others getting spotted.
Unfortunately their is no pb command in podbot.cfg to switch it on/off.
Not yet
But you can use "mp_flashlight 0" if the flashing bots make you crazy.
Of course then you can't use it yourself anymore + you have to type it again after every map change.