Merge pull request #46636 from nmshelke/fix-55759

mgr/volumes: subvolume ls command crashes if groupname as '_nogroup'

Reviewed-by: Venky Shankar <vshankar@redhat.com>
Reviewed-by: Ramana Raja <rraja@redhat.com>
Reviewed-by: Kotresh HR <khiremat@redhat.com>

diff --cc qa/tasks/cephfs/test_volumes.py
Simple merge

diff --cc src/pybind/mgr/volumes/fs/operations/group.py
Simple merge