Be less verbose in download

The wget usually success, so we don't need to know everything
about it. Also redirect STDERR to STDOUT, so that the output
appears in order.
Use tenant admin credentials for uploading images

Glance in Juno does not allow non-tenant-admins to upload
images anymore.
Switch to the non-deprecated glance command line

The command line that we used was already deprecated in
Essex and it seems support for that broke now in Juno.
Lets update it.