Cleanup #43700: cephadm: make it a proper python package
cephadm: move bin/cephadm from the git tree to download.ceph.com
Right now, people are downloading cephadm directly from the source tree.
curl --silent --remote-name --location https://github.com/ceph/ceph/raw/pacific/src/cephadm/cephadm
This prevents us from automatically assembling the cephadm binary in any form.
If we want to have a chance to compile or zip or assemble the cephadm binary, We need to move away from the git source tree.