Run Zookeeper container with user 'zookeeper' instead of 'root'

[janhoy]

Change log description

Makes Zookeeper container run as user zookeeper instead of as 'root'

Purpose of the change

Fixes #538

What the code does

Changes user in Dockerfile

How to verify it

Build the image and run Zookeeper. Verify that it runs as user zookeeper.

TODO: The zookeeper POD needs fsGroup: 1000 for this to work, so the mounted data PVC with be owned by the zookeeper group.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.12%. Comparing base (9d283c2) to head (137ed8f).
⚠️ Report is 9 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #561   +/-   ##
=======================================
  Coverage   85.12%   85.12%           
=======================================
  Files          12       12           
  Lines        1613     1613           
=======================================
  Hits         1373     1373           
  Misses        155      155           
  Partials       85       85           

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[janhoy]

Consolidating all commands in the same RUN will save one Docker layer. While it would probably work to keep these files owned by root it is clearer to let the user own them, as is the case for all files in the upstream image.