[Development] Moving to Gerrit 2.16.9

[Frederik Gladhorn]

Hi,

Just to keep the ball rolling, we prepared the upgrade to move from Gerrit 
2.16.7 to 2.16.9. I don't expect any real changes, but it's a good exercise 
for us to stay up to date and see if the scripting of the upgrade works.
The only real challenge was upgrading Bazel, since every Gerrit version seems 
to only compile with one exact Bazel version (roughly).

So far it seems to work nicely for me, running the script which stops gerrit, 
pushes the new release and restarts it takes around two minutes, so there 
won't be any significant downtime this time around.

Assuming there are no big concerns I'll just do the upgrade tomorrow, on the 
test instance it works without problems.

On a related note, now that things are generally working with the new Gerrit, 
I was wondering if we want to consider plugins. There is one to add reviewers 
based on git blame
https://gerrit-review.googlesource.com/admin/repos/plugins/reviewers-by-blame
and I'll give Gravatar a spin:
https://gerrit-review.googlesource.com/admin/repos/plugins/avatars-gravatar

We should also consider the various webhooks plugins. Comments appreciated.

Cheers,
Frederik