Moved ssh_check to role specific functions

- Moved ssh_check() to configure_{master,slave} in configuration.py
- This help relieves check during node add.

Signed-off-by: Shashank Sahni <shredder12@gmail.com>
Add node feature added

- Created add_nodes() in cluster.py
- Created Job API for add request
- Created add() in job.py
- Updated job_test.sh

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