[SPARK-8954] [BUILD] Remove unneeded deb repository from Dockerfile to fix build error in docker.

[SPARK-8954] [Build]
1. Remove unneeded deb repository from Dockerfile to fix build error in docker.
2. Remove unneeded /var/lib/apt/lists/* after install to reduce the docker image size (by ~30MB).

Author: yongtang <yongtang@users.noreply.github.com>

Closes #7346 from yongtang/SPARK-8954 and squashes the following commits:

36024a1 [yongtang] [SPARK-8954] [Build] Remove unneeded /var/lib/apt/lists/* after install to reduce the docker image size (by ~30MB)
7084941 [yongtang] [SPARK-8954] [Build] Remove unneeded deb repository from Dockerfile to fix build error in docker.

docker/spark-test/base/Dockerfile

@@ -17,13 +17,13 @@
 
 FROM ubuntu:precise
 
-RUN echo "deb http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list
-
 # Upgrade package index
-RUN apt-get update
-
 # install a few other useful packages plus Open Jdk 7
-RUN apt-get install -y less openjdk-7-jre-headless net-tools vim-tiny sudo openssh-server
+# Remove unneeded /var/lib/apt/lists/* after install to reduce the
+# docker image size (by ~30MB)
+RUN apt-get update && \
+    apt-get install -y less openjdk-7-jre-headless net-tools vim-tiny sudo openssh-server && \
+    rm -rf /var/lib/apt/lists/*
 
 ENV SCALA_VERSION 2.10.4
 ENV CDH_VERSION cdh4