[Minor] Register some missing symbols

src/plugins/lua/asn.lua

       parent = id,
       type = 'virtual',
       flags = 'empty',
+      score = 0,
     })
   end
 else

src/plugins/lua/greylist.lua

       callback = greylist_set,
       priority = 6,
     })
-    rspamd_config:register_symbol({
+    local id = rspamd_config:register_symbol({
       name = 'GREYLIST_CHECK',
       type = 'prefilter',
       callback = greylist_check,
       priority = 6,
     })
+    rspamd_config:register_symbol({
+      name = settings.symbol,
+      type = 'virtual',
+      parent = id,
+      score = 0,
+    })
   end
 end