Fixing dockerhub build.

The latest debian:jessie image doesn't seem to like the command
"apt-get remove --purge -y `apt-mark showauto`".
It tries to remove a number of important base packages.
It doesn't seem to save a lot of space anyway.

Change-Id: If55b319f7d74698398d76650fa1c4a8d8475bb63
(cherry picked from commit 9bdf5da497920b6e4c0d163e65bc1f9337f2af8f)
diff --git a/Dockerfile b/Dockerfile
index 6ab7673..45186a2 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -24,8 +24,6 @@
         cp buck-out/gen/tools/package/onos-package/onos.tar.gz /tmp/ && \
         cd .. && \
         rm -rf onos && \
-        apt-get remove --purge -y `apt-mark showauto` && \
-        apt-get install oracle-java8-set-default -y && \
         apt-get clean && apt-get purge -y && apt-get autoremove -y && \
         rm -rf /var/lib/apt/lists/* && \
         rm -rf /var/cache/oracle-jdk8-installer