overlay: create workdir if it doesn't exist
overlay: create workdir if it doesn't exist

Otherwise a container created before we needed workdir will fail
to start after a kernel+lxc update.

Signed-off-by: Serge Hallyn <3df611b026e4639bee8aef7a4beb2e39fcebb313@ubuntu.com>
Acked-by: KATOH Yasufumi <512423cb3a4857a38f472862b51e4ab1a1730f06@jazz.email.ne.jp>

yubo/lxc,efiop/lxc,bostjan/lxc,yubo/lxc,lazy404/lxc,Ponce/lxc,caglar10ur/lxc,raspberrypython/lxc,virajs/lxc,thmo/lxc,federicobriata/lxc,bmoar/lxc,ysbnim/lxc,tych0/lxc,Distrotech/lxc,Pelagicore/lxc,efiop/lxc,akshaykarle/lxc,sapun/lxc,raspberrypython/lxc,bmoar/lxc,rldleblanc/lxc,caglar10ur/lxc,cjwatson/lxc,hallyn/lxc,QingweiPeterLan/cs188-lxc,thmo/lxc,armcc/lxc,GreatFruitOmsk/lxc,terceiro/lxc,cjwatson/lxc,GreatFruitOmsk/lxc,ksperis/lxc,christiaan/lxc,major/lxc,hallyn/lxc,lisongmin/lxc,federicobriata/lxc,thmo/lxc,rldleblanc/lxc,LynxChaus/lxc,akshaykarle/lxc,Distrotech/lxc,ecarrara/lxc,bmoar/lxc,akshaykarle/lxc,szaszg/lxc,hfuCN/lxc,christiaan/lxc,major/lxc,lisongmin/lxc,DarknessBeforeDawn/lxc,LynxChaus/lxc,LynxChaus/lxc,federicobriata/lxc,rldleblanc/lxc,ksperis/lxc,armcc/lxc,ecarrara/lxc,DarknessBeforeDawn/lxc,jirislaby/lxc,GreatFruitOmsk/lxc,hkjolhede/lxc,bostjan/lxc,codebauss/lxc,hkjolhede/lxc,cjwatson/lxc,lazy404/lxc,sapun/lxc,JohnPeacockMessageSystems/lxc,aeris/lxc,ioops/lxc,codebauss/lxc,JohnPeacockMessageSystems/lxc,DarknessBeforeDawn/lxc,armcc/lxc,sapun/lxc,tych0/lxc,jirislaby/lxc,ss1h2a3tw/lxc,terceiro/lxc,hkjolhede/lxc,QingweiPeterLan/cs188-lxc,jirislaby/lxc,Distrotech/lxc,major/lxc,ioops/lxc,ksperis/lxc,Pelagicore/lxc,christiaan/lxc,szaszg/lxc,terceiro/lxc,Pelagicore/lxc,ss1h2a3tw/lxc,yubo/lxc,bostjan/lxc,rowhit/lxc,lisongmin/lxc,fwilson42/lxc,caglar10ur/lxc,szaszg/lxc,rowhit/lxc,Ponce/lxc,hfuCN/lxc,ysbnim/lxc,ysbnim/lxc,JohnPeacockMessageSystems/lxc,QingweiPeterLan/cs188-lxc,raspberrypython/lxc,fwilson42/lxc,ioops/lxc,aeris/lxc,codebauss/lxc,hfuCN/lxc,lazy404/lxc,virajs/lxc,hallyn/lxc,efiop/lxc,ecarrara/lxc,rowhit/lxc,Ponce/lxc,aeris/lxc,virajs/lxc,tych0/lxc,ss1h2a3tw/lxc,fwilson42/lxc