security/py-netmiko: Update to 3.3.0

• Modernize "do-test" target while I'm here.

Note: Although there are already newer releases out here, use this one
because the newer releases depend on some Python packages that have yet
to be ported.

Changelogs since 3.1.1:

https://github.com/ktbyers/netmiko/releases/tag/v3.3.0
https://github.com/ktbyers/netmiko/releases/tag/v3.2.0

MFH: 2021Q3