Do not attempt installing reform-qcacld2 in the background if inside chroot

If this script is not run on a real system with a real init process but in a container-like chroot environment, then creating these background processes without waiting for their completion will leave zombie processes behind which hog resources like /dev/null and thus prevent the container software from cleanly un-mounting bind-mounts as they may have been created for /dev/null. We cannot reliably detect whether the container manager will automatically wait for and reap zombie processes, so as a hacky workaround, we just make this script a no-op if it is started inside a chroot environment.

Finding out that the reform-qcacld2 kernel postinst snippet was responsible for my container manager to fail took quite a bit of time...