Merge branch 'stable-2.16' into stable-3.0

* stable-2.16:
  ReadOnlyByHttpIT: Extend to cover both 'readonly' and 'readonly~readonly'
  ReadOnlyByHttpIT: Extend assertions on response content
  ReadOnly: Format with google-java-format
  Allow endpoint "config/server/readonly"
  REST: Report state from PUT and DELETE

Change-Id: I0e421ad7990a4cfea2c7f2ea0fef30f3fe7887c1