nft-restore: Fix for deletion of new, referenced rule

nft-restore: Fix for deletion of new, referenced rule

Combining multiple corner-cases here:

* Insert a rule before another new one which is not the first. Triggers
  NFTNL_RULE_ID assignment of the latter.

* Delete the referenced new rule in the same batch again. Causes
  overwriting of the previously assigned RULE_ID.

Consequently, iptables-nft-restore fails during *insert*, because the
reference is dangling.

Reported-by: Eric Garver <eric@garver.life>
Fixes: 760b35b46e4cc ("nft: Fix for add and delete of same rule in single batch")
Signed-off-by: Phil Sutter <phil@nwl.cc>
Tested-by: Eric Garver <eric@garver.life>