ct timeout: fix 'list object x' vs. 'list objects in table' confusion

ct timeout: fix 'list object x' vs. 'list objects in table' confusion

<empty ruleset>
$ nft list ct timeout table t
Error: No such file or directory
list ct timeout table t
                      ^
This is expected to list all 'ct timeout' objects.
The failure is correct, the table 't' does not exist.

But now lets add one:
$ nft add table t
$ nft list ct timeout  table t
Segmentation fault (core dumped)

... and thats not expected, nothing should be shown
and nft should exit normally.

Because of missing TIMEOUTS command enum, the backend thinks
it should do an object lookup, but as frontend asked for
'list of objects' rather than 'show this object',
handle.obj.name is NULL, which then results in this crash.

Update the command enums so that backend knows what the
frontend asked for.

Signed-off-by: Florian Westphal <fw@strlen.de>