fix demo ci bug

1. trt_demo bug
2. trigger exit when exists a bug

test=develop

paddle/fluid/inference/api/demo_ci/run.sh

@@ -116,6 +116,10 @@ D
       --modeldir=$DATA_DIR/mobilenet/model \
       --data=$DATA_DIR/mobilenet/data.txt \
       --refer=$DATA_DIR/mobilenet/result.txt 
+    if [ $? -ne 0 ]; then
+      echo "trt demo trt_mobilenet_demo runs fail."
+      exit 1
+    fi
   fi
 done
 set +x

paddle/fluid/inference/api/demo_ci/trt_mobilenet_demo.cc

@@ -38,8 +38,8 @@ void Main() {
   std::unique_ptr<PaddlePredictor> predictor;
   paddle::contrib::AnalysisConfig config;
   config.EnableUseGpu(100, 0);
-  config.SetModel(FLAGS_modeldir + "/__params__",
-                  FLAGS_modeldir + "/__model__");
+  config.SetModel(FLAGS_modeldir + "/__model__",
+                  FLAGS_modeldir + "/__params__");
   config.EnableTensorRtEngine();
   predictor = CreatePaddlePredictor(config);