Bump cirros version to 0.6.1

Cirros has made a fresh release, let us use it. Switch the download URLs
to https and drop an old example that no longer is available.

Depends-On: https://review.opendev.org/c/openstack/tempest/+/871271
Change-Id: I1d391b871fc9bfa825db30db9434922226b94d8a
2 files changed