Now we have terminals for instance and group clusters we can remove the
FF now. Deploying to group clusters has been working without complaints
too.

With this MR, group clusters is now functional, so default to enabled.

Have a single setting on the root ancestor group to enabled or disable
group clusters feature as a whole

Mayra Cabrera authored 6 years ago and Thong Kuah committed 6 years ago

As the frontend is still in progress and other related backend is still
in prgress we need a feature flag to turn off Group Clusters.

- Add pages javascripts to intialize clusters for group pages

- Move specs asserting gcp specific validations from controller into
UpdateService spec

- Also teach Clusters::ApplicationController about groups