openssh: move nftable rule to staging layer Tested: image booted with qemu and rule is present Fusion-Link: https://fusion2.corp.google.com/5fd45600-cead-3853-af48-f57d0000f1ee Google-Bug-Id: N/A Change-Id: I710315e18ff8e946288fdfbc95bbe239a1c7386a Signed-off-by: Yuxiao Zhang <yuxiaozhang@google.com>