This pins the version of helm-toolkit used in the build due to
a breaking change in helm-toolkit.
Once helm 2.13.1 is released with this fix [0] we can update to use
it, and update the helm-toolkit pin to "master".
[0]: https://github.com/helm/helm/pull/5411
Change-Id: I827f1145c6d670cc955b82155455455a4f3ca486