lxc-ps to limit its search to containers
lxc-ps to limit its search to containers

The purpose of this patch is to limit the search
of pids to those in containers by looking at first
in the /cgroup/<name>/tasks  when --lxc or --names options
are specified by user.
The idea is to speedup the output when only few
container names are specified while the machine
is running with many processes.

Signed-off-by: Michel Normand <10b15bce2c7509208f200eeee988f2b52225636e@free.fr>
Signed-off-by: Daniel Lezcano <3211518dd4d87cb3f7ee12cb52e14b7fb2bc0446@fr.ibm.com>

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