Deleted EOF control in telnet sync/async control chars

[lorenzo-d-m]

Description

PR related to issue #351.

The EOF sequence control has been added to telnet transport in PR #143 (Dmitriy's issue #142 ), however, after Matt's contribution, the EOF control can be removed from the _handle_control_chars method.

Also, connecting devices like Cisco PIX and some old ASA, that control raised the scrapli.exceptions.ScrapliConnectionNotOpened: server returned EOF, connection not opened exception. And it shouldn't.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

I tested my update on a dozen devices, some of which inserted the EOF sequence in the middle of the stream, some at the end of the stream, and some did not. In all cases it worked well.

Checklist:

• My code follows the style guidelines of this project (no GitHub actions complaints! run make lint before
  committing!)
• I have commented my code, pydocstyle and darglint are happy, docstrings are in google docstring format, and all
  docstrings include a summary, args, returns and raises fields (even if N/A)
• New and existing unit tests pass locally with my changes

[carlmontanari]

blah. I still need to fix whatever that mypy complaint is, so ignore that. LGTM, thanks a bunch for digging in and testing this up!