Detecting open Dropbear server

[Captain-T2004]

Checklist

• [x] I have followed the Contributor Guidelines.
• [ ] The code has been thoroughly tested in my local development environment with flake8 and pylint.
• [x] The code is Python 3 compatible.
• [x] The code follows the PEP8 styling guidelines with 4 spaces indentation.
• [x] This Pull Request relates to only one issue or only one feature
• [x] I have referenced the corresponding issue number in my commit message
• [x] I have added the relevant documentation.
• [x] My branch is up-to-date with the Upstream master branch.

Changes proposed in this pull request

This pull request solves issue #715, Due to internal workings of Paramiko library used to connect to SSH in core_ssh.py, Nettacker was unable to detect an open passwordless SSH server. Adding an exception fixes that problem. But to be on the safe side i have added an empty line to the default passwords list(Nettacker/lib/payloads/passwords/top_1000_common_passwords.txt).

Your development environment

• OS: Pop-OS
• OS Version: 22.04
• Python Version: 3.10