cache: accumulate flags in batch

cache: accumulate flags in batch

commit 68c8fb5f7c988a38a694c77c65e789e0cb8dfd8a upstream.

Recent updates are relaxing cache requirements:

  babc6ee8773c ("cache: populate chains on demand from error path")

Flags describe cache requirements for a given batch, accumulate flags
that are inferred from commands in this batch.

Fixes: 7df42800cf89 ("src: single cache_update() call to build cache before evaluation")
Tested-by: Eric Garver <eric@garver.life>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>