Cleanup parts of lxc-destroy
Cleanup parts of lxc-destroy

A bit of pedantry usually doesn't hurt. The code should be easier to follow now
and avoids some repetitions.

Signed-off-by: Christian Brauner <94aca18939fc64aa4df96ea8cb026da8a2e1541a@gmail.com>
Acked-by: Serge E. Hallyn <3df611b026e4639bee8aef7a4beb2e39fcebb313@ubuntu.com>

ss1h2a3tw/lxc,aeris/lxc,cjwatson/lxc,aeris/lxc,LynxChaus/lxc,Distrotech/lxc,QingweiPeterLan/cs188-lxc,DarknessBeforeDawn/lxc,thmo/lxc,DarknessBeforeDawn/lxc,thmo/lxc,ksperis/lxc,hallyn/lxc,thmo/lxc,ss1h2a3tw/lxc,Ponce/lxc,armcc/lxc,hfuCN/lxc,caglar10ur/lxc,aeris/lxc,ksperis/lxc,QingweiPeterLan/cs188-lxc,caglar10ur/lxc,fwilson42/lxc,tych0/lxc,tych0/lxc,GreatFruitOmsk/lxc,terceiro/lxc,ysbnim/lxc,hfuCN/lxc,armcc/lxc,ksperis/lxc,ss1h2a3tw/lxc,cjwatson/lxc,cjwatson/lxc,federicobriata/lxc,DarknessBeforeDawn/lxc,hfuCN/lxc,federicobriata/lxc,bostjan/lxc,armcc/lxc,LynxChaus/lxc,akshaykarle/lxc,GreatFruitOmsk/lxc,fwilson42/lxc,terceiro/lxc,hallyn/lxc,QingweiPeterLan/cs188-lxc,LynxChaus/lxc,GreatFruitOmsk/lxc,bostjan/lxc,Ponce/lxc,akshaykarle/lxc,Distrotech/lxc,Ponce/lxc,tych0/lxc,ysbnim/lxc,bostjan/lxc,caglar10ur/lxc,Distrotech/lxc,ysbnim/lxc,hallyn/lxc,akshaykarle/lxc,fwilson42/lxc,terceiro/lxc,federicobriata/lxc