The _get_ssh_connection in ssh.py retries to connect without a sleep

The code in _get_ssh_connection in ssh.py retries to connect without a sleep in case of socket error.

This can cause a SYN attack.
The retries shall be implemented as an exponential back-off.

    def _get_ssh_connection(self):
        """Returns an ssh connection to the specified host."""
        _timeout = True
(...)

        while not self._is_timed_out(self.timeout, _start_time):
            try:
                ssh.connect(self.host, username=self.username,
                            password=self.password,
                            look_for_keys=self.look_for_keys,
                            key_filename=self.key_filename,
                            timeout=self.timeout, pkey=self.pkey)
                _timeout = False
                break
            except socket.error:
                continue
            except paramiko.AuthenticationException:
                time.sleep(5)
                continue