cmd/k8s-operator: enable IP forwarding without the sysctl binary (#20768)

The sysctler init container shells out to sysctl to turn on IP
forwarding for non-userspace proxies. That binary ships in the
procps-ng package, which Alpine has but Red Hat's UBI does not, so
on UBI the init container exits 127 and every proxy Pod is stuck in
PodInitializing and never registers a device.

Updates: https://github.com/tailscale/corp/issues/45981
Updates: https://github.com/tailscale/corp/issues/44443

Signed-off-by: David Bond <davidsbond93@gmail.com>