qa/suites/upgrade/telemetry-upgrade/reef-x: update how cephadm is pulled and change...

qa/suites/upgrade/telemetry-upgrade/reef-x: update how cephadm is pulled and change image reference

Update how cephadm is pulled:

`cephadm_git_url` and `cephadm_branch` are used in releases older than reef
to install cephadm. Both of these keys are needed to install it from the github
repo.

However, in reef and on, the compiled zipapp cephadm needs to be pulled differently
than the old single python script `cephadm` from earlier releases.

This commit is what I referenced for this change: https://github.com/ceph/ceph/commit/967716f2e6c8cd3f7d810a5f8e5e49448717e513

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Change image reference:

`quay.io/ceph/daemon-base:latest-reef` points to the latest reef tag (v18.2.2),
not the tip of reef, which is actually what we want to test.

Pulling the daemon-base:latest-reef image shows it is running v18.2.2:
```
lflores:ceph$ podman run --rm -it daemon-base:latest-reef
[root@d4d9a0eb04be /]# ceph -v
ceph version 18.2.2 (531c0d11a1c5d39fbfe6aa8a521f023abf3bf3e2) reef (stable)
```

It is important that we test the tip of reef in case there is a fix there that we
want to pick up.

I referenced this commit to make the change: https://github.com/ceph/ceph/commit/d0381ed7e68a6de7c9ff1e4220698ed8eab28ac6

Signed-off-by: Laura Flores <lflores@ibm.com>