Forced fsGroup when using cache breaks Renovate deployments in restricted environments

[minijus]

After the change that adds fsGroup automatically (#1404) chart deployments on restricted environments (e.g. OpenShift) started to fail.

In OpenShift containers run as non root with random user id and directories with mounted volumes are automatically chown'ed. Thus, statically setting fsGroup is not an option in OpenShift.

Proposed solution to overcome this issue would be to introduce additional value compatability.omitSecurityContextFsGroup (or any other proposed name). The default for new value would be false and if it is as true the chart would omit fsGroup property.

Happy to open PR for this (after deciding on possible solution/naming).