need_to_install_distro(): return newest version
need_to_install_distro(): return newest version

Signed-off-by: Zack Cerza <d7cdf09fc0f0426e98c9978ee42da5d61fa54986@redhat.com>

zhouyuan/teuthology,ivotron/teuthology,michaelsevilla/teuthology,michaelsevilla/teuthology,ceph/teuthology,caibo2014/teuthology,dreamhost/teuthology,ivotron/teuthology,dmick/teuthology,dmick/teuthology,robbat2/teuthology,ktdreyer/teuthology,SUSE/teuthology,SUSE/teuthology,dreamhost/teuthology,robbat2/teuthology,SUSE/teuthology,ktdreyer/teuthology,caibo2014/teuthology,ceph/teuthology,dmick/teuthology,zhouyuan/teuthology