pyhton-common: fix mypy errors

pyhton-common: fix mypy errors

Fixes:

```
py3 run-test: commands[2] | mypy --config-file=../mypy.ini -p ceph
ceph/deployment/service_spec.py: note: In member "yaml_representer" of class "ServiceSpec":
ceph/deployment/service_spec.py:659: error: Argument 1 to "represent_dict" of "SafeRepresenter" has incompatible type "_OrderedDictItemsView[str, Any]"; expected "Mapping[Any, Any]"
```

Signed-off-by: Sebastian Wagner <sewagner@redhat.com>
(cherry picked from commit 73e7698958d1cfacf1abb35fcd36f5849b55fd15)