security/py-netmiko: Update to 2.4.2

Changelog:

• Add Keymile driver
• Fix session_log corruption bug
• Add support for ProxyJump in SSH config file
• Add support for Linux prompt terminators via environment variables

Note: Barring critical bugs this should be the last Netmiko release that

will support Python 2.

https://github.com/ktbyers/netmiko/releases/tag/v2.4.2