lxc_start: ERROR if container is already running.
lxc_start: ERROR if container is already running.

We should exit with a error when starting a running container.

Signed-off-by: Dongsheng Yang <1b957dfff8d0f16ed124fab3c79d8c1232c34692@cn.fujitsu.com>
Acked-by: Serge E. Hallyn <3df611b026e4639bee8aef7a4beb2e39fcebb313@ubuntu.com>

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