Make docker volumes work with SELinux in enforcing mode

[zenofile]

Currently, when running on a host OS where SELinux is in Enforcing mode, files inside docker volumes cannot be read due to insufficient permissions with AVC denials piling up in the audit log.

With a minor modification to https://github.com/cupcakearmy/autorestic/blob/6990bf6adc200e7e5a38e76e8f07c4060d3650f1/internal/backend.go#L161-L167 adding --security-opt label=disable to disable label separation for the autorestic container, everything works as intended.

Tested with podman instead of docker.