changed the default value of resv_IDs to None

Signed-off-by: Shashank Sahni <shredder12@gmail.com>
Integrated chef for Hadoop configuration

* Removed the old method implemented in connectoMaster.
* Called Knife commands using subprocess module.
* Implemented asynchronous provisioning and configuration of cluster using
multiprocessing module.

Signed-off-by: Shashank Sahni <shredder12@gmail.com>