devel/py-buildbot{-*}: Update to 2.2.0

buildbot:

• Now python 3 only (3.5+)
• Add missing tests_requires to setup.py

buildbot-worker:

• Retains Python 2/3 compatibility
• Remove setup.py patch (upstreamed)

Changelog:

https://docs.buildbot.net/current/relnotes/index.html#buildbot-2-2-0-2019-04-07

Security: 5536ea5f-6814-11e9-a8f7-0050562a4d7b
MFH: 2019Q2