Add cuda 8/9.1 centos 6 builds, test GPU wheel on CPU only container. (#3309)

* Add cuda 8/9.1 centos 6 builds, test GPU wheel on CPU only container.

* Add Google test

tests/ci_build/Dockerfile.release

@@ -0,0 +1,34 @@
+FROM centos:6
+
+# Environment
+ENV DEBIAN_FRONTEND noninteractive
+
+# Install all basic requirements
+RUN \
+    yum -y update && \
+    yum install -y wget graphviz && \
+    # Python
+    wget https://repo.continuum.io/miniconda/Miniconda2-4.3.27-Linux-x86_64.sh && \
+    bash Miniconda2-4.3.27-Linux-x86_64.sh -b -p /opt/python
+
+ENV PATH=/opt/python/bin:$PATH
+
+# Install Python packages
+RUN \
+    conda install numpy scipy pandas matplotlib nose scikit-learn && \
+    pip install nose wheel auditwheel graphviz
+
+ENV GOSU_VERSION 1.10
+
+# Install lightweight sudo (not bound to TTY)
+RUN set -ex; \
+    wget -O /usr/local/bin/gosu "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-amd64" && \
+    chmod +x /usr/local/bin/gosu && \
+    gosu nobody true
+
+# Default entry-point to use if running locally
+# It will preserve attributes of created files
+COPY entrypoint.sh /scripts/
+
+WORKDIR /workspace
+ENTRYPOINT ["/scripts/entrypoint.sh"]