ping the AssetClient from the agent

assignment-client/src/Agent.cpp

@@ -403,6 +403,7 @@ void Agent::sendPingRequests() {
         case NodeType::AvatarMixer:
         case NodeType::AudioMixer:
         case NodeType::EntityServer:
+        case NodeType::AssetClient:
             return true;
         default:
             return false;