No error message for the invalid credential for the ssh plugin

[mkumatag]

if wrong private key is supplied, it just keeps on trying and prints message as Fetching IP for machine, there is no clue what is happening. Need further discussion to understand how we can enhance the error message.

different values for following fields:

            "key_pair_name": "mkumatag-pub-key",
            "ssh_private_key_file": "/Users/manjunath/.ssh/id_rsa",