cephadm: remove duplicates when listing files in scan

Fix running tox env flake8 during a rebase/merge where git ls-files
may return duplicate file names.

An earlier version of this change used the `--deuplicate` option to `git
ls-files` in order to remove duplicate files listed when running the
tool during rebase/merge. Mysteriously, this seemed to break the `ceph
API tests` in the CI. A completely unrelated command in a tox file that,
AFAIK, is not executed in that test suite. They ways of git are
subtle and often sucky.

Signed-off-by: John Mulligan <[email protected]>

src/cephadm/tox.ini

@@ -62,7 +62,7 @@ deps =
     flake8-quotes
 commands =
     flake8 --config=tox.ini {posargs:cephadm.py cephadmlib}
-    bash -c 'test $(git ls-files 'cephadm.py' 'cephadmlib/*.py' | xargs grep "docker.io" | wc -l) == 11'
+    bash -c 'test $(git ls-files 'cephadm.py' 'cephadmlib/*.py' | sort -u | xargs grep "docker.io" | wc -l) == 11'
 # Downstream distributions may choose to alter this "docker.io" number,
 # to make sure no new references to docker.io are creeping in unnoticed.