Reverting change to install OpenJDK 7 on analytics nodes.

See:
http://wiki.apache.org/hadoop/HadoopJavaVersions
http://www.cloudera.com/content/cloudera-content/cloudera-docs/CDH4/latest/CDH4-Release-Notes/cdh4rn_topic_2_2.html

"Note*: OpenJDK6 has some open bugs w.r.t handling of generics (https://bugs.launchpad.net/ubuntu/+source/openjdk-6/+bug/611284, https://bugs.launchpad.net/ubuntu/+source/openjdk-6/+bug/716959), so OpenJDK cannot be used to compile hadoop mapreduce code in branch-0.23 and beyond, please use other JDKs."

"MRv2 (YARN) is not supported on JDK 7 at present, because of MAPREDUCE-2264. This problem is expected to be fixed in an upcoming release."

Change-Id: I36a3e7df237021723e2a04d669c099f319dddf69
Merge "Reverting change to install OpenJDK 7 on analytics nodes." into production