evaluate: bail out if new flowtable does not specify hook and priority

evaluate: bail out if new flowtable does not specify hook and priority

commit 5ad475fce5a138d3a8b58bde4a41b0537d15b952 upstream.

If user forgets to specify the hook and priority and the flowtable does
not exist, then bail out:

 # cat flowtable-incomplete.nft
 table t {
  flowtable f {
   devices = { lo }
  }
 }
 # nft -f /tmp/k
 flowtable-incomplete.nft:2:12-12: Error: missing hook and priority in flowtable declaration
 flowtable f {
           ^

Update one existing tests/shell to specify a hook and priority.

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