Fix for MAINT-7787: [Alex Ivy] RC Viewers in 5.1.0 range show black background...

Fix for MAINT-7787: [Alex Ivy] RC Viewers in 5.1.0 range show black background for CONTENT_TYPE_HTML. (The color we pass to CEF has 4 compontents red, blue, green and alpha.  We were only passing 3 and setting the color and not the alpha. At somepoint in CEF's history the default value must have changed. Passing 0xFF for alpha too - i.e. fully opaque - fixes this)

indra/media_plugins/cef/media_plugin_cef.cpp

@@ -448,7 +448,7 @@ void MediaPluginCEF::receiveMessage(const char* message_string)
 
 				dullahan::dullahan_settings settings;
 				settings.accept_language_list = mHostLanguage;
-				settings.background_color = 0xffffff;
+				settings.background_color = 0xffffffff;
 				settings.cache_enabled = true;
 				settings.cache_path = mCachePath;
 				settings.cookie_store_path = mCookiePath;