packet-couchbase.c: dissect more DCP commands

Change-Id: I0e06c89cdda3c1f8e98412fd20737ff6afd26666
Reviewed-on: https://code.wireshark.org/review/5694
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Michael Mann <mmann78@netscape.net>
Petri-Dish: Michael Mann <mmann78@netscape.net>
Reviewed-by: Anders Broman <a.broman58@gmail.com>