Download centos base image instead of fuel/centos
Download centos base image instead of fuel/centos

CentOS base docker image is a dependency for 
fuel-centos-build container. It was left out
in commit b975019fabdb429c1869047df18dd792d2163ecc.
Change-Id: I822a6bb8c32f6592adc8971c1d67ca80af354e45
Partial-Bug: #1428060

AnselZhangGit/fuel-main,zhaochao/fuel-main,teselkin/fuel-main,ddepaoli3/fuel-main-dev,AnselZhangGit/fuel-main,zhaochao/fuel-main,eayunstack/fuel-main,SergK/fuel-main,Fiware/ops.Fuel-main-dev,SergK/fuel-main,dancn/fuel-main-dev,stackforge/fuel-main,SmartInfrastructures/fuel-main-dev,dancn/fuel-main-dev,SmartInfrastructures/fuel-main-dev,eayunstack/fuel-main,huntxu/fuel-main,ddepaoli3/fuel-main-dev,stackforge/fuel-main,teselkin/fuel-main,AnselZhangGit/fuel-main,stackforge/fuel-main,teselkin/fuel-main,Fiware/ops.Fuel-main-dev,eayunstack/fuel-main,AnselZhangGit/fuel-main,SmartInfrastructures/fuel-main-dev,zhaochao/fuel-main,ddepaoli3/fuel-main-dev,Fiware/ops.Fuel-main-dev,SmartInfrastructures/fuel-main-dev,SergK/fuel-main,zhaochao/fuel-main,teselkin/fuel-main,huntxu/fuel-main,zhaochao/fuel-main,ddepaoli3/fuel-main-dev,huntxu/fuel-main,dancn/fuel-main-dev,dancn/fuel-main-dev,Fiware/ops.Fuel-main-dev