Fix how disallow_iframe_embed is defined

The disallow_iframe_embed option doesn't belong to HORIZON_CONFIG but
should be described as a variable in local_settings.

Closes-Bug: #1942722
Change-Id: I189fbb0a76ba63e16f6c3b6ad9db6f9e0355617f
(cherry picked from commit 7153d5cdfa)

releasenotes/notes/bug-1942722-3cc45ac696688336.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Fixed wrong usage of the ``DISALLOW_IFRAME_EMBED`` option.

spec/classes/horizon_init_spec.rb

@@ -209,6 +209,7 @@ describe 'horizon' do
           'COMPRESS_OFFLINE = False',
           "FILE_UPLOAD_TEMP_DIR = '/var/spool/horizon'",
           "OVERVIEW_DAYS_RANGE = 1",
+          'DISALLOW_IFRAME_EMBED = True',
         ])
       end
 
@@ -573,16 +574,16 @@ describe 'horizon' do
       end
     end
 
-    context 'with disallow iframe embed enabled' do
+    context 'with disallow iframe embed disabled' do
       before do
         params.merge!({
-                        :disallow_iframe_embed => true
+                        :disallow_iframe_embed => false
                       })
       end
 
       it 'disallow_iframe_embed is configured' do
         verify_concat_fragment_contents(catalogue, 'local_settings.py', [
-                                          'HORIZON_CONFIG["disallow_iframe_embed"] = True',
+                                          'DISALLOW_IFRAME_EMBED = False',
                                         ])
       end
     end

templates/local_settings.py.erb

@@ -1025,9 +1025,7 @@ REST_API_REQUIRED_SETTINGS = ['OPENSTACK_HYPERVISOR_FEATURES',
 # For more information see:
 # http://tinyurl.com/anticlickjack
 #DISALLOW_IFRAME_EMBED = True
-<% if @disallow_iframe_embed == true %>
-HORIZON_CONFIG["disallow_iframe_embed"] = True
-<% end %>
+DISALLOW_IFRAME_EMBED = <%= @disallow_iframe_embed.to_s.capitalize %>
 
 <% if @horizon_upload_mode %>
 HORIZON_IMAGES_UPLOAD_MODE = <%= @horizon_upload_mode %>