Revert "cache: recycle existing cache with incremental updates"

Revert "cache: recycle existing cache with incremental updates"

This reverts commit e791dbe109b6dd891a63a4236df5dc29d7a4b863.

Eric Garver reported two issues:

- index with rule breaks, because NFT_CACHE_REFRESH is missing.
- simple set updates.

Moreover, the current process could populate the cache with objects for
listing commands (no generation ID is bumped), while another process
could update the ruleset. Leading to a inconsistent cache due to the
genid + 1 check.

This optimization needs more work and more tests for -i/--interactive,
revert it.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>