Fix all users of CredentialsController to provide vm-scope

Introduced in #425, `CredentialsController` needs a `vm-scope` attribute to be able to determine the correct scope.

This change was not done in app/views/layouts/angular/_auth_service_account_angular.html.haml which caused adding a GCE provider to be broken.

Fixing.

app/views/layouts/angular/_auth_service_account_angular.html.haml

@@ -4,7 +4,7 @@
 - vm_scope ||= false
 - main_scope = vm_scope ? "$parent.vm" : "$parent"
 
-%div{"ng-controller" => "CredentialsController"}
+%div{"ng-controller" => "CredentialsController", "vm-scope" => main_scope}
   %div{"ng-show" => ng_show}
     .form-group{"ng-class" => "{'has-error': angularForm.service_account.$invalid}"}
       %label.col-md-2.control-label{"for" => "service_account"}