[FAB-1411] Pull the zookeeper tarball by curl

Pull the zookeeper tarball by using curl instead of wget, so it can
understand the "socks*://" style proxy protocol prefixes, yet support
wget's "http*://" scheme.

Not exactly the FAB-1411 but closely relate to.

Extract the archive using a pipeline, which avoid leaving the allocated
space of the archive as dark matter in the image's layers (and reduce
code length BTW).

Change-Id: I2cf8f04f7ba98c99ceeb2befe8d92c78b8b9e332
Signed-off-by: Ray Chen <ray@hyperchain.cn>

images/zookeeper/Dockerfile.in

@@ -29,10 +29,8 @@ ARG DISTRO_NAME=zookeeper-3.4.9
 # Download Apache Zookeeper, verify its PGP signature, untar and clean up
 RUN set -x \
     && cd / \
-    && wget -q "http://www.apache.org/dist/zookeeper/$DISTRO_NAME/$DISTRO_NAME.tar.gz" \
-    && tar -xzf "$DISTRO_NAME.tar.gz" \
-    && mv "$DISTRO_NAME/conf/"* "$ZOO_CONF_DIR" \
-    && rm -r "$DISTRO_NAME.tar.gz"
+    && curl -fsSL "http://www.apache.org/dist/zookeeper/$DISTRO_NAME/$DISTRO_NAME.tar.gz" | tar -xz \
+    && mv "$DISTRO_NAME/conf/"* "$ZOO_CONF_DIR"
 
 WORKDIR $DISTRO_NAME
 VOLUME ["$ZOO_DATA_DIR", "$ZOO_DATA_LOG_DIR"]