[Docker] Slim down autoscaler image (#8683)

* Modifed dockerfiles for base-deps and autoscaler

* Reverted base-deps to use xenial instead of bionic, reverted addition of gnupg2

* Added --no-cache-dir to pip install

Co-authored-by: jenkins-x-bot <jenkins-x@googlegroups.com>

docker/autoscaler/Dockerfile

@@ -2,22 +2,26 @@ FROM rayproject/base-deps
 ARG WHEEL_PATH
 ARG WHEEL_NAME
 
-RUN apt update
-RUN apt install -y curl tmux screen rsync apt-transport-https
-
 # Install kubectl.
-RUN curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
-RUN touch /etc/apt/sources.list.d/kubernetes.list
-RUN echo "deb http://apt.kubernetes.io/ kubernetes-xenial main" | tee -a /etc/apt/sources.list.d/kubernetes.list
-RUN apt update
-RUN apt install -y kubectl
+RUN apt-get update \
+    && apt-get install -y curl \
+                        tmux \
+                        screen \
+                        rsync \
+                        apt-transport-https \
+    && curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add - \
+    && touch /etc/apt/sources.list.d/kubernetes.list \
+    && echo "deb http://apt.kubernetes.io/ kubernetes-xenial main" | tee -a /etc/apt/sources.list.d/kubernetes.list \
+    && apt-get update \
+    && apt install -y kubectl \
+    && apt-get clean 
 
 # We have to uninstall wrapt this way for Tensorflow compatibility
 COPY requirements.txt .
-RUN pip install -r requirements.txt
-
 COPY $WHEEL_PATH $WHEEL_NAME
-RUN pip install $WHEEL_NAME[all]
+
+RUN pip --no-cache-dir install -r requirements.txt \
+    && pip --no-cache-dir install $WHEEL_NAME[all]
 
 # For Click
 ENV LC_ALL=C.UTF-8

docker/base-deps/Dockerfile

@@ -22,14 +22,12 @@ RUN apt-get update \
     && /opt/conda/bin/conda install -y \
         libgcc python=3.6.9 \
     && /opt/conda/bin/conda clean -y --all \
-    && /opt/conda/bin/pip install \
+    && /opt/conda/bin/pip install --no-cache-dir \
         flatbuffers \
         cython==0.29.0 \
-        numpy==1.15.4
-        
-
-# To avoid the following error on Jenkins:
-# AttributeError: 'numpy.ufunc' object has no attribute '__module__'
-RUN /opt/conda/bin/pip uninstall -y dask
+        numpy==1.15.4 \
+    # To avoid the following error on Jenkins:
+    # AttributeError: 'numpy.ufunc' object has no attribute '__module__'
+    && /opt/conda/bin/pip uninstall -y dask
 
 ENV PATH "/opt/conda/bin:$PATH"