src: Better error reporting if chain type is invalid

src: Better error reporting if chain type is invalid

This patch verifies at command line parsing that given chain type
is valid. Possibilities are: filter, nat, and route.

nft add chain test test { type cheese hook input priority 0 };
<cmdline>:1:28-33: Error: unknown chain type cheese
add chain test test { type cheese hook input priority 0 };
                           ^^^^^^

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>