lxc_destroy: be quiet if asked
lxc_destroy: be quiet if asked

As per https://bugs.launchpad.net/bugs/1543016.

Signed-off-by: Serge Hallyn <3df611b026e4639bee8aef7a4beb2e39fcebb313@ubuntu.com>

terceiro/lxc,hfuCN/lxc,hallyn/lxc,terceiro/lxc,federicobriata/lxc,caglar10ur/lxc,QingweiPeterLan/cs188-lxc,thmo/lxc,caglar10ur/lxc,tych0/lxc,ss1h2a3tw/lxc,terceiro/lxc,caglar10ur/lxc,GreatFruitOmsk/lxc,ysbnim/lxc,aeris/lxc,LynxChaus/lxc,ysbnim/lxc,QingweiPeterLan/cs188-lxc,akshaykarle/lxc,GreatFruitOmsk/lxc,ss1h2a3tw/lxc,LynxChaus/lxc,tych0/lxc,thmo/lxc,aeris/lxc,hfuCN/lxc,GreatFruitOmsk/lxc,LynxChaus/lxc,hallyn/lxc,ysbnim/lxc,cjwatson/lxc,cjwatson/lxc,federicobriata/lxc,thmo/lxc,hfuCN/lxc,hallyn/lxc,QingweiPeterLan/cs188-lxc,akshaykarle/lxc,tych0/lxc,ss1h2a3tw/lxc,aeris/lxc,cjwatson/lxc,federicobriata/lxc,akshaykarle/lxc