ceph: remove auth in osd-purge job
ceph: remove auth in osd-purge job

`ceph osd purge` should remove the OSD auth, but many users have issues
where they are unable to create new OSDs after removing old ones due to
the old OSD auth still being present. Therefore, run `ceph auth del` for
the OSD after purging to fix this.

Signed-off-by: Blaine Gardner <135b86f2968bdbcc730c10d8ababd343bb675986@redhat.com>

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