(canary) Creating Kubernetes Cluster - cannot fetch Google project billing status

### Summary

When creating a new Kubernetes Cluster, and I select a project from the "Google Cloud Platform project" field, the request to Google is blocked by CSP.

### Steps to reproduce

* Turn on canary with by setting the `gitlab_canary` cookie
* Go to Operations, Kubernetes
* Select "Create new Cluster on GKE"
* select any project from the "Google Cloud Platform project" field

### Example Project

https://gitlab.com/tkuah/test_rails/clusters/new

### What is the current *bug* behavior?

The "Google Cloud Platform project" field is stuck on "Validating project billing status" and cannot be selected anymore.

### What is the expected *correct* behavior?

We successfully validate the project billing status, and the field shows the GCP project that was selected by the user.

### Relevant logs and/or screenshots

Console shows the following error :

```
Refused to frame 'https://content-cloudbilling.googleapis.com/' because it violates the following Content Security Policy directive: "frame-src 'self' https://www.google.com/recaptcha/ https://content.googleapis.com https://content-cloudresourcemanager.googleapis.com".
```

![Screen_Shot_2018-07-17_at_11.11.39_AM](/uploads/b9221ae2e5369f906115d9701d7c0188/Screen_Shot_2018-07-17_at_11.11.39_AM.png)

With `gitlab_canary`, I receive the following header for https://gitlab.com/tkuah/test_rails/clusters/new :

```
Content-Security-Policy: object-src 'none'; worker-src https://assets.gitlab-static.net https://gl-canary.global.ssl.fastly.net https://gitlab.com blob:; script-src 'self' 'unsafe-inline' 'unsafe-eval' https://assets.gitlab-static.net https://gl-canary.global.ssl.fastly.net https://www.google.com/recaptcha/ https://www.gstatic.com/recaptcha/ https://apis.google.com; style-src 'self' 'unsafe-inline' https://assets.gitlab-static.net https://gl-canary.global.ssl.fastly.net; img-src * data: blob:; frame-src 'self' https://www.google.com/recaptcha/ https://content.googleapis.com https://content-cloudresourcemanager.googleapis.com; frame-ancestors 'self'; connect-src 'self' https://assets.gitlab-static.net https://gl-canary.global.ssl.fastly.net wss://gitlab.com https://sentry.gitlap.com https://customers.gitlab.com; report-uri https://sentry-infra.gitlap.com/api/3/csp-report/?sentry_key=a664fdde83424b43a991f25fa7c78987

```

Without `gitlab_canary` :

```
Content-Security-Policy: object-src 'none'; worker-src https://assets.gitlab-static.net https://gitlab.com blob:; script-src 'self' 'unsafe-inline' 'unsafe-eval' https://assets.gitlab-static.net https://www.google.com/recaptcha/ https://www.gstatic.com/recaptcha/ https://apis.google.com; style-src 'self' 'unsafe-inline' https://assets.gitlab-static.net; img-src * data: blob:; frame-src 'self' https://www.google.com/recaptcha/ https://content.googleapis.com https://content-compute.googleapis.com https://content-cloudbilling.googleapis.com https://content-cloudresourcemanager.googleapis.com; frame-ancestors 'self'; connect-src 'self' https://assets.gitlab-static.net wss://gitlab.com https://sentry.gitlap.com https://customers.gitlab.com; report-uri https://sentry-infra.gitlap.com/api/3/csp-report/?sentry_key=a664fdde83424b43a991f25fa7c78987

```

So somehow, the canary servers are missing `https://content-cloudbilling.googleapis.com` from the CSP header

### Output of checks

This bug happens on GitLab.com

### Possible fixes

Add the above src to the `frame-src` CSP directive.

Story points: 1.0