fix e_shelf_position_calc() to not set struct members before applying them
fix e_shelf_position_calc() to not set struct members before applying them

fix T2743

tasn/enlightenment,tizenorg/platform.upstream.enlightenment,rvandegrift/e,tasn/enlightenment,tizenorg/platform.upstream.enlightenment,tizenorg/platform.upstream.enlightenment,tasn/enlightenment,rvandegrift/e,rvandegrift/e