Save only the required attributes from other nodes instead of saving the node objects. Refer req #308. This also fixes req #307
Merge pull request #316 from bijugs/fix_req_308

Fix for req #308 & #307
Make YARN auto-tuning for nodemanager available memory, VCPU's
Make YARN scheduler an attribute to allow easy choosing between fair-scheduler or capacity-scheduler
Ensure ulimits are respected for hdfs, hbase, mapreduce and yarn
Ensure kafka has a reasonable open file ulimit
Stop being draconian with IPv6 and simply tell Java to prefer IPv4 where needed
Move to tracking upstream sysctl cookbook again