Prepare the underlying SSH connection with the remote target.

def _prepare_connection(**kwargs):
    '''
    Prepare the underlying SSH connection with the remote target.
    '''
    paramiko_kwargs, scp_kwargs = _select_kwargs(**kwargs)
    ssh = paramiko.SSHClient()
    if paramiko_kwargs.pop('auto_add_policy', False):
        ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    ssh.connect(**paramiko_kwargs)
    scp_client = scp.SCPClient(ssh.get_transport(),
                               **scp_kwargs)
    return scp_client