fix build bug (#859)

deploy/cpp/scripts/bootstrap.sh

 # download pre-compiled opencv lib
-#OPENCV_URL=https://bj.bcebos.com/paddleseg/deploy/opencv3.4.6gcc4.8ffmpeg.tar.gz2
-#if [ ! -d "./deps/opencv3.4.6gcc4.8ffmpeg/" ]; then
-#    mkdir -p deps
-#    cd deps
-#    wget -c ${OPENCV_URL}
-#    tar xvfj opencv3.4.6gcc4.8ffmpeg.tar.gz2
-#    cd ..
-#fi
-OPENCV_URL=https://paddleseg.bj.bcebos.com/deploy/docker/opencv3gcc4.8.tar.bz2
-if [ ! -d "./deps/opencv3gcc4.8" ]; then
+OPENCV_URL=https://bj.bcebos.com/paddleseg/deploy/opencv3.4.6gcc4.8ffmpeg.tar.gz2
+if [ ! -d "./deps/opencv3.4.6gcc4.8ffmpeg/" ]; then
     mkdir -p deps
     cd deps
     wget -c ${OPENCV_URL}
-    tar xvfj opencv3gcc4.8.tar.bz2
-    rm -rf opencv3gcc4.8.tar.bz2
+    tar xvfj opencv3.4.6gcc4.8ffmpeg.tar.gz2
     cd ..
 fi