Fix name reuse issues for actors, and make luprex IDs more readable

luprex/cpp/core/eng-tests.cpp

@@ -107,7 +107,6 @@ public:
 
     RunUnitTests() {
         world_.reset(new World(WORLD_TYPE_MASTER));
-        stop_driver();
         rescan_lua_source(true);
     }
 
@@ -116,6 +115,7 @@ public:
             case AccessKind::INVOKE_LUA_SOURCE: {
                 world_->update_source(datapk);
                 world_->run_unittests();
+                stop_driver();
                 break;
             }
             default: break;