commands.c: sanity check to not write too-long cgroup path name
commands.c: sanity check to not write too-long cgroup path name

This can't really happen due to current limits in cgroup.c but add it
in case those change in the future.

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

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