src: add cache level flags

src: add cache level flags

The score approach based on command type is confusing.

This patch introduces cache level flags, each flag specifies what kind
of object type is needed. These flags are set on/off depending on the
list of commands coming in this batch.

cache_is_complete() now checks if the cache contains the objects that
are needed through these new flags.

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