rbd: include original namespace type in "rbd snap ls --all" output

rbd: include original namespace type in "rbd snap ls --all" output

Before (snap 22 comes from "rbd group snap create", snap 23 created
manually with "rbd snap create"):

SNAPID  NAME                                  SIZE   PROTECTED  TIMESTAMP                 NAMESPACE
    21  f7cfdcfe-5f71-40e4-be82-3fb0e7caf2aa  1 GiB             Mon Jun 10 09:23:40 2024  trash (mysnap)
    22  bd67397f-32cb-48fe-b1ac-ef6f02319239  1 GiB             Mon Jun 10 09:26:06 2024  trash (.group.2_1491b049b556_1497bf66f586)
    23  27a5f053-8431-428e-ab33-be9d8b6cf51e  1 GiB             Mon Jun 10 09:28:30 2024  trash (.group.2_1491b049b556_1497bf66f586)

After:

SNAPID  NAME                                  SIZE   PROTECTED  TIMESTAMP                 NAMESPACE
    21  f7cfdcfe-5f71-40e4-be82-3fb0e7caf2aa  1 GiB             Mon Jun 10 09:23:40 2024  trash (user mysnap)
    22  bd67397f-32cb-48fe-b1ac-ef6f02319239  1 GiB             Mon Jun 10 09:26:06 2024  trash (group .group.2_1491b049b556_1497bf66f586)
    23  27a5f053-8431-428e-ab33-be9d8b6cf51e  1 GiB             Mon Jun 10 09:28:30 2024  trash (user .group.2_1491b049b556_1497bf66f586)

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>