exmdb_client: add back special localhost handling for homeserver 0

Fixes: gromox-3.4-156-g2a748fee3

Author: jengelh

exch/exmdb/parser.cpp

@@ -103,7 +103,7 @@ static bool exmdb_parser_is_local(const char *prefix, bool *pvt)
 		mlog(LV_ERR, "%s: %s: %s", __func__, prefix, strerror(err));
 		return false;
 	}
-	if (hostname == g_host_id)
+	if (hostname == g_host_id || hostname.empty())
 		return true;
 	mlog(LV_DEBUG, "exmdb: is_local: %s not served here (%s) (but at %s)",
 		prefix, g_host_id.c_str(), hostname.c_str());

lib/exmdb_client.cpp

@@ -482,6 +482,8 @@ static remote_conn_ref exmdb_client_get_connection(const char *dir)
 			mlog(LV_ERR, "exmdb_client: cannot find remote server for %s", dir);
 			return fc;
 		}
+		if (itm.host.empty())
+			itm.host = "localhost";
 		itm.type = is_pvt ? remote_svr::EXMDB_PRIVATE : remote_svr::EXMDB_PUBLIC;
 		sv_hold.lock();
 		mdcl_server_list.emplace_back(std::move(itm));