Changes

Remove several unused containers

* alpine-*: looks like they were never used
* debian-{jessie,stretch}-*: EOL
* debian9-repo-install-test: EOL
* gitolite: never used? / upstream container last updated 3 years ago
* osmo-gerrit-libosmo: unused example from 2017, based on jessie
* patchwork: looks like never used, ancient version
* public-inbox: added in 2018 for playing around, apparently unused
* tmp: unfinished and unused
* ubuntu-zesty-build: was added for testing ubuntu 17.04, unused

Related: OS#5601
Change-Id: Ic09046379ddff049629bb66850ead7ba479c4450