cephadm: silence "Failed to evict container" log msg

cephadm: silence "Failed to evict container" log msg

Right now, we're printing some evil looking messages in the log:

```
systemd[1]: Starting Ceph mgr.node2.ankmgz for ...
podman[32354]: Error: no container with name or ID ceph-... found: no such container
bash[32363]: Error: Failed to evict container: "": Failed to find container "ceph-..." in state: no container with name or ID ceph-... found: no such container
bash[32363]: Error: no container with ID or name "ceph-..." found: no such container
````

Also, the unit.run command already removes the container. No need
for ExecStartPre to do the same.

Signed-off-by: Sebastian Wagner <sebastian.wagner@suse.com>