Lazily init DBus only when it is needed
Lazily init DBus only when it is needed

OpenShift has some cAdvisor packages in its import chain. The init() here
invokes Dbus start even when cAdvisor is not actively running or being
used (in our packages).  This change makes the systemd check and dbus
initialization and connection lazy, occuring only the first time someone
invokes UseSystemd().

cnaize/cadvisor,wulonghui/cadvisor,aivarasko/cadvisor,ainsleyc/cadvisor,feiskyer/cadvisor,aivarasko/cadvisor,kmicheal/cadvisor,ncdc/cadvisor,dchen1107/cadvisor,dchen1107/cadvisor,ncdc/cadvisor,f0/cadvisor,hzy001/cadvisor,anarcher/cadvisor,pwittrock/cadvisor,atyenoria/cadvisor,timstclair/cadvisor,carmark/cadvisor,c-st/cadvisor,jimonreal/cadvisor,hw-qiaolei/cadvisor,guoshimin/cadvisor,bing6/cadvisor,feiskyer/cadvisor,mangalaman93/cadvisor,aivarasko/cadvisor,BrickXu/cadvisor,derwolfe/cadvisor,BrickXu/cadvisor,derekwaynecarr/cadvisor,mesosphere/cadvisor,hw-qiaolei/cadvisor,vegasbrianc/cadvisor,linux-on-ibm-z/cadvisor,IFTTT/cadvisor,jimmidyson/cadvisor,mangalaman93/cadvisor,mesosphere/cadvisor,c-st/cadvisor,c-st/cadvisor,mr-justin/cadvisor,f0/cadvisor,hw-qiaolei/cadvisor,difro/cadvisor,yolkov/cadvisor,hacpai/cadvisor,takecy/cadvisor,vishh/cadvisor,ChengTiesheng/cadvisor,normanjoyner/cadvisor,CrazyJvm/cadvisor,derekwaynecarr/cadvisor,f0/cadvisor,bpradipt/cadvisor,wulonghui/cadvisor,datawisesystems/cadvisor,atyenoria/cadvisor,jzaefferer/cadvisor,Clever/cadvisor,Clever/cadvisor,jhjeong-kr/cadvisor,bpradipt/cadvisor,mr-justin/cadvisor,BrickXu/cadvisor,pwittrock/cadvisor,jmaitrehenry/cadvisor,afein/cadvisor,bowlofstew/cadvisor,erSitzt/cadvisor,yolkov/cadvisor,guoshimin/cadvisor,jmaitrehenry/cadvisor,jhjeong-kr/cadvisor,ncdc/cadvisor,takecy/cadvisor,morpheyesh/cadvisor,jimonreal/cadvisor,pwittrock/cadvisor,vishh/cadvisor,kmicheal/cadvisor,jimonreal/cadvisor,carmark/cadvisor,derekwaynecarr/cadvisor,vegasbrianc/cadvisor,rajthilakmca/cadvisor,wulonghui/cadvisor,megamsys/cadvisor,dchen1107/cadvisor,whosthatknocking/cadvisor,feiskyer/cadvisor,rajthilakmca/cadvisor,vegasbrianc/cadvisor,jhjeong-kr/cadvisor,morpheyesh/cadvisor,cnaize/cadvisor,dalanlan/cadvisor,yolkov/cadvisor,mr-justin/cadvisor,whosthatknocking/cadvisor,IFTTT/cadvisor,CrazyJvm/cadvisor,hzy001/cadvisor,BrickXu/cadvisor,erSitzt/cadvisor,timstclair/cadvisor,afein/cadvisor,jimmidyson/cadvisor,rajthilakmca/cadvisor,dalanlan/cadvisor,timstclair/cadvisor,ainsleyc/cadvisor,jmaitrehenry/cadvisor,dchen1107/cadvisor,erSitzt/cadvisor,IFTTT/cadvisor,ncdc/cadvisor,jzaefferer/cadvisor,cnaize/cadvisor,derwolfe/cadvisor,hacpai/cadvisor,f0/cadvisor,IFTTT/cadvisor,ChengTiesheng/cadvisor,bing6/cadvisor,yifan-gu/cadvisor,IFTTT/cadvisor,shilpamayanna/cadvisor,bowlofstew/cadvisor,Clever/cadvisor,derekwaynecarr/cadvisor,Snorch/cadvisor,Snorch/cadvisor,erSitzt/cadvisor,guoshimin/cadvisor,jimmidyson/cadvisor,mesosphere/cadvisor,megamsys/cadvisor,linux-on-ibm-z/cadvisor,jhjeong-kr/cadvisor,ainsleyc/cadvisor,CrazyJvm/cadvisor,mangalaman93/cadvisor,anarcher/cadvisor,f0/cadvisor,linux-on-ibm-z/cadvisor,hzy001/cadvisor,atyenoria/cadvisor,derekwaynecarr/cadvisor,bing6/cadvisor,ChengTiesheng/cadvisor,yifan-gu/cadvisor,bowlofstew/cadvisor,takecy/cadvisor,erSitzt/cadvisor,dchen1107/cadvisor,kmicheal/cadvisor,difro/cadvisor,normanjoyner/cadvisor,shilpamayanna/cadvisor,bpradipt/cadvisor,whosthatknocking/cadvisor,Snorch/cadvisor,jhjeong-kr/cadvisor,BrickXu/cadvisor,datawisesystems/cadvisor,yifan-gu/cadvisor,jzaefferer/cadvisor,derwolfe/cadvisor,dalanlan/cadvisor,hacpai/cadvisor,vishh/cadvisor,difro/cadvisor,anarcher/cadvisor,ainsleyc/cadvisor,ncdc/cadvisor