Check if stdout is a terminal in lxc-checkconfig
Check if stdout is a terminal in lxc-checkconfig

Let lxc-checkconfig write to non-tty stdout without color control
characters
Signed-off-by: walkerning <8fa81238203014072301298ad18550e5153a8c1a@gmail.com>

caglar10ur/lxc,cjwatson/lxc,QingweiPeterLan/cs188-lxc,ysbnim/lxc,caglar10ur/lxc,cjwatson/lxc,caglar10ur/lxc,hallyn/lxc,terceiro/lxc,hfuCN/lxc,aeris/lxc,hallyn/lxc,hfuCN/lxc,QingweiPeterLan/cs188-lxc,GreatFruitOmsk/lxc,thmo/lxc,GreatFruitOmsk/lxc,ss1h2a3tw/lxc,GreatFruitOmsk/lxc,LynxChaus/lxc,federicobriata/lxc,terceiro/lxc,LynxChaus/lxc,federicobriata/lxc,hallyn/lxc,ss1h2a3tw/lxc,terceiro/lxc,ysbnim/lxc,thmo/lxc,LynxChaus/lxc,aeris/lxc,ss1h2a3tw/lxc,aeris/lxc,federicobriata/lxc,cjwatson/lxc,ysbnim/lxc,QingweiPeterLan/cs188-lxc,hfuCN/lxc,thmo/lxc