clean up base Dockerfile
clean up base Dockerfile

- run "yum update" after installing RDO repository (to ensure we get any
  package updates from this repository)
- "yum clean" after the "yum update" to prevent yum cache from being
  baked into the image

Change-Id: Id897fd85214855bb08f7e16da4bbdf07b821d991

mandre/kolla,HackToday/kolla,jakedahn/kolla,intel-onp/kolla,toby82/kolla,bdastur/kolla,fdumpling/kolla,stackforge/kolla,chenzhiwei/kolla,thetrav/kolla,negronjl/kolla,invenfantasy/kolla,mandre/kolla,bdastur/kolla,negronjl/kolla,toby82/kolla,invenfantasy/kolla,rajalokan/kolla,limamauricio/mykolla,negronjl/kolla,limamauricio/mykolla,brk3/kolla,stackforge/kolla,coolsvap/kolla,HackToday/kolla,rahulunair/kolla,dardelean/kolla-ansible,jasonbrooks/kolla,openstack/kolla,nihilifer/kolla,rajalokan/kolla,LoHChina/kolla,jakedahn/kolla,stackforge/kolla,openstack/kolla,mandre/kolla,jasonbrooks/kolla,GalenMa/kolla,fdumpling/kolla,thetrav/kolla,meticulo3366/kolla,brk3/kolla,LoHChina/kolla,invenfantasy/kolla,toby82/kolla,chenzhiwei/kolla,chenzhiwei/kolla,rajalokan/kolla,coolsvap/kolla,dardelean/kolla-ansible,limamauricio/mykolla,meticulo3366/kolla,GalenMa/kolla,dardelean/kolla-ansible,mrangana/kolla,LoHChina/kolla,mrangana/kolla,rahulunair/kolla,intel-onp/kolla,tonyli71/kolla,coolsvap/kolla,HackToday/kolla,tonyli71/kolla,fdumpling/kolla,jakedahn/kolla,nihilifer/kolla