Indeed, this is a hard requirement for the embedded Elasticsearch. And running Elasticsearch on ACI is known to be tricky.
Unfortunately, I have no easy solution to offer you right now 
. You could try and contact Azure support, or search for solutions on how to run Elasticsearch on ACI. The same (or at least, similar) solution would apply to running SonarQube, although it may require you create a custom image, which extends the official one.
If you do find a solution, we’d love to hear about it.