Attempting to build the documentation with "tox -e docs" results in a
failure due to several lint errors. This patch fixes those errors so
that the docs build successfully.
The 'docs' target is also added to the 'linters' target chain so that
the doc8 linting is executed as part of the lint checks to ensure that
these issues don't re-occur.
Change-Id: I9e1bf2cabe9a0591963d1afadbeb24cb614e0b27
2b422dbad1