Fix bug when using multiple DeployArtifactURLs
Fix bug when using multiple DeployArtifactURLs

The script tries to download all artifact URLs with a single
request, instead of downloading each URL on its own if
multiple DeployArtifactURLs were given.

Change-Id: I6a8be699aff7023a67702bb1d3ddc2273984cd08

openstack/tripleo-heat-templates,openstack/tripleo-heat-templates,dprince/tripleo-heat-templates,dprince/tripleo-heat-templates