This commit introduces a non-voting job to lint Helm charts against the
latest version of Helm toolkit from OpenStack-Helm Infra. This job
should serve as an indicator of when it's safe to advance the version of
Helm toolkit used by Airship.
Additionally, this commit modifies all Helm chart lint jobs to run on
each commit, regardless of the files modified by a change. This should
not introduce a noticeable difference in CI runtime, as these jobs
execute quicker than the tox jobs.
Change-Id: I90473fd73a740f2711eb85e131edfa457944ea5e
ed489d2c81