[PATCH nft v2] evaluate: fix "list set" unexpected behaviour

["Pablo M. Bermudo Garay" <pablombg@gmail.com>]

Special sets like maps and flow tables have their own commands to be
listed and inspected.

Before this patch, "nft list set" was able to display these special sets
content:

  # nft list set filter test
  table ip filter {
          map test {
                  type ipv4_addr : inet_service
                  elements = { 192.168.1.101 : http-alt}
          }
  }

Now an error is shown:

  # nft list set filter test
  <cmdline>:1:1-20: Error: Could not process rule: Set 'test' does not exist
  list set filter test
  ^^^^^^^^^^^^^^^^^^^^

Signed-off-by: Pablo M. Bermudo Garay <pablombg@gmail.com>
---
 src/evaluate.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/evaluate.c b/src/evaluate.c
index 423523f..f24e5f3 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -2674,7 +2674,8 @@ static int cmd_evaluate_list(struct eval_ctx *ctx, struct cmd *cmd)
 		if (table == NULL)
 			return cmd_error(ctx, "Could not process rule: Table '%s' does not exist",
 					 cmd->handle.table);
-		if (set_lookup(table, cmd->handle.set) == NULL)
+		set = set_lookup(table, cmd->handle.set);
+		if (set == NULL || set->flags & (SET_F_MAP | SET_F_EVAL))
 			return cmd_error(ctx, "Could not process rule: Set '%s' does not exist",
 					 cmd->handle.set);
 		return 0;
-- 
2.8.3