Updated cluster API, support for multiple slaves

* Updated Cluster API to include node objects and multiple slaves.
* Simplified _create_cluster()
* Included a flush_data_to_mongo() function to update cluster
document in mongo
* Updated cluster_test script as per the new API format

Signed-off-by: Shashank Sahni <shredder12@gmail.com>
Updated delete to follow new API

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

Blocked Master bootstrap by using subprocess.call to ensure
master daemons' up and running before bootstrapping slaves.

Signed-off-by: Shashank Sahni <shredder12@gmail.com>
Instance metadata fail handled in ssh_check

* Catching paramiko.SSHException in ssh_check() to avoid crash
during an instance metadata failure(key injection).
* Added code in configure_cluster to abort if the exception occurs
for the master node. For the rest it continues.

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