remove get-image.sh
remove get-image.sh

switching to centos-7 atomic host, which already includes
docker and kubernetes (etc), so the get-image.sh script is no longer
necessary.

projectatomic/heat-kubernetes,v1k0d3n/heat-kubernetes,mdshuai/heat-kubernetes,yuanying/heat-kubernetes,jamesmarva/heat-kubernetes,larsks/heat-kubernetes,rootfs/heat-kubernetes