HADOOP-13307. add rsync to Dockerfile so that precommit archive works. Contributed by Allen Wittenauer.

(cherry picked from commit 85209cc59152bcd7070b0a654af7d64105d36a6b)

dev-support/docker/Dockerfile

@@ -57,6 +57,7 @@ RUN apt-get update && apt-get install --no-install-recommends -y \
     python \
     python2.7 \
     pylint \
+    rsync \
     snappy \
     zlib1g-dev