Use FQDN in downburst yaml.
Use FQDN in downburst yaml.

As newer rhel's like to default to localdomain screwing with things
if its not set. Older cloud-init/distros appear to just ignore the
domain.

Signed-off-by: Sandon Van Ness <a38d61b815b8053a15c463c80449b5c080334ec7@redhat.com>

caibo2014/teuthology,robbat2/teuthology,yghannam/teuthology,t-miyamae/teuthology,robbat2/teuthology,dmick/teuthology,SUSE/teuthology,dreamhost/teuthology,ceph/teuthology,SUSE/teuthology,dmick/teuthology,zhouyuan/teuthology,tchaikov/teuthology,SUSE/teuthology,ceph/teuthology,zhouyuan/teuthology,ktdreyer/teuthology,tchaikov/teuthology,michaelsevilla/teuthology,caibo2014/teuthology,ivotron/teuthology,dreamhost/teuthology,dmick/teuthology,t-miyamae/teuthology,yghannam/teuthology,ktdreyer/teuthology,ivotron/teuthology,michaelsevilla/teuthology