The 'docs' tox target executes the doc8 lint test which may result in
failures when testing documentation builds, but OpenStack-CI does not
execute that tox target.
In order to ensure that we catch all standard documentation syntax
errors and prevent them from merging, this patch includes the docs
target in the 'linters' chain of tests.
Fixes for any failures which result from executing this test are also
included in the patch.
Change-Id: Iba9a6d7611354d5734858e9f3771958af1a23a9d
bfef87c954