Helm value appImageTag is overwritten by chart version

[pascal-holy]

Current Behaviour

In the helm release process, we rely on this sed to change the version of each of our sub-charts to correspond to the current version of the release.

Proposed Solution

Change the helm template to default to the appImageTag and fall back on the chart version. This requires setting the appImageTag to the release version during helm install which might be tricky depending on the background of the helm install