Include cloud-platform scope as a supported scope

The cloud-platform scope grants access to r/w data for all GCP services,
so it should work.

Change-Id: I9757bb77aa375d8a59add1bd6c52160fcbb14651

git-cookie-authdaemon

diff --git a/git-cookie-authdaemon b/git-cookie-authdaemon
index 536e011..1b85291 100755
--- a/git-cookie-authdaemon
+++ b/git-cookie-authdaemon
@@ -38,6 +38,7 @@
 
 META_URL = 'http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/'
 SUPPORTED_SCOPES = [
+  'https://www.googleapis.com/auth/cloud-platform',
   'https://www.googleapis.com/auth/gerritcodereview',
   'https://www.googleapis.com/auth/source.full_control',
   'https://www.googleapis.com/auth/source.read_write',