Arvados

The keep_services table has been obsolete since Arvados 2.0 -- the keep_services/accessible endpoint returns the services listed in the config file instead.

Except: when test suites bring keepstore/keepproxy services up and down, they rely on the keep_services/accessible controller to return the contents of the keep_services table when it's not empty.

We should fix this so we can remove the keep_services table entirely, as well as the ARVADOS_USE_KEEP_ACCESSIBLE_API env var introduced in #21773.

When changing keepproxy/keepstore setup in run_test_servers.py, we should update the config file and restart (or SIGHUP, if we add support for that) existing keepproxy/keepstore processes as needed so they all use the new port numbers and other config settings.

We started to deal with this in #21773 but punted.