[SPARK-10398] [DOCS] Migrate Spark download page to use new lua mirroring scripts

Migrate Apache download closer.cgi refs to new closer.lua

This is the bit of the change that affects the project docs; I'm implementing the changes to the Apache site separately.

Author: Sean Owen <sowen@cloudera.com>

Closes #8557 from srowen/SPARK-10398.

docker/spark-mesos/Dockerfile

@@ -24,7 +24,7 @@ RUN apt-get update && \
     apt-get install -y python libnss3 openjdk-7-jre-headless curl
 
 RUN mkdir /opt/spark && \
-    curl http://www.apache.org/dyn/closer.cgi/spark/spark-1.4.0/spark-1.4.0-bin-hadoop2.4.tgz \
+    curl http://www.apache.org/dyn/closer.lua/spark/spark-1.4.0/spark-1.4.0-bin-hadoop2.4.tgz \
     | tar -xzC /opt
 ENV SPARK_HOME /opt/spark
 ENV MESOS_NATIVE_JAVA_LIBRARY /usr/local/lib/libmesos.so

docs/running-on-mesos.md

@@ -45,7 +45,7 @@ frameworks.  You can install Mesos either from source or using prebuilt packages
 To install Apache Mesos from source, follow these steps:
 
 1. Download a Mesos release from a
-   [mirror](http://www.apache.org/dyn/closer.cgi/mesos/{{site.MESOS_VERSION}}/)
+   [mirror](http://www.apache.org/dyn/closer.lua/mesos/{{site.MESOS_VERSION}}/)
 2. Follow the Mesos [Getting Started](http://mesos.apache.org/gettingstarted) page for compiling and
    installing Mesos