This change corrects many problems detected by the `yamllint` linter.
It's a preparation for enabling this linter in change
For instance, the first run of the YAML linter helped discovering a key
duplication problem in `oso_ha.yaml`: the `depends_on` key was present
twice, so the first occurence was ignored.
Other changes are cosmetic: extra spaces, extra blank lines, missing
newlines at end-of-file, etc.