MUC: Fix delay@from to be room JID (fixes #1416)

plugins/muc/history.lib.lua

@@ -178,10 +178,10 @@ module:hook("muc-add-history", function(event)
 	local ts = gettime();
 	local stamp = datetime.datetime(ts);
 	stanza:tag("delay", { -- XEP-0203
-		xmlns = "urn:xmpp:delay", from = module.host, stamp = stamp
+		xmlns = "urn:xmpp:delay", from = room.jid, stamp = stamp
 	}):up();
 	stanza:tag("x", { -- XEP-0091 (deprecated)
-		xmlns = "jabber:x:delay", from = module.host, stamp = datetime.legacy()
+		xmlns = "jabber:x:delay", from = room.jid, stamp = datetime.legacy()
 	}):up();
 	local entry = { stanza = stanza, timestamp = ts };
 	table.insert(history, entry);