Revert CI upgrade.

Author: trivialfis

Jenkinsfile

@@ -119,7 +119,7 @@ def ClangTidy() {
     echo "Running clang-tidy job..."
     def container_type = "clang_tidy"
     def docker_binary = "docker"
-    def dockerArgs = "--build-arg CUDA_VERSION=10.1"
+    def dockerArgs = "--build-arg CUDA_VERSION=9.2"
     sh """
     ${dockerRun} ${container_type} ${docker_binary} ${dockerArgs} python3 tests/ci_build/tidy.py
     """

tests/ci_build/Dockerfile.clang_tidy

@@ -7,16 +7,14 @@ ENV DEBIAN_FRONTEND noninteractive
 # Install all basic requirements
 RUN \
     apt-get update && \
-    wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add - && \
-    add-apt-repository -u 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic main' && \
-    apt-get install -y tar unzip wget git build-essential python3 python3-pip llvm-10 clang-tidy-10 clang-10 && \
+    apt-get install -y tar unzip wget git build-essential python3 python3-pip llvm-7 clang-tidy-7 clang-7 && \
     wget -nv -nc https://cmake.org/files/v3.12/cmake-3.12.0-Linux-x86_64.sh --no-check-certificate && \
     bash cmake-3.12.0-Linux-x86_64.sh --skip-license --prefix=/usr
 
 # Set default clang-tidy version
 RUN \
-    update-alternatives --install /usr/bin/clang-tidy clang-tidy /usr/bin/clang-tidy-10 100 && \
-    update-alternatives --install /usr/bin/clang clang /usr/bin/clang-10 100
+    update-alternatives --install /usr/bin/clang-tidy clang-tidy /usr/bin/clang-tidy-7 100 && \
+    update-alternatives --install /usr/bin/clang clang /usr/bin/clang-7 100
 
 # Install Python packages
 RUN \