mgr/volumes: place getters and setters next to each other

mgr/volumes: place getters and setters next to each other

workaround for mypy issue:
https://github.com/python/mypy/issues/1465

fixes mypy errors:

volumes/fs/operations/group.py: note: In class "Group":
volumes/fs/operations/group.py:44: error: Name 'uid' already defined on line 36
volumes/fs/operations/group.py:44: error: "Callable[[Group], Any]" has no attribute "setter"
volumes/fs/operations/group.py:48: error: Name 'gid' already defined on line 40
volumes/fs/operations/group.py:48: error: "Callable[[Group], Any]" has no attribute "setter"

volumes/fs/operations/group.py: note: In function "open_group":
volumes/fs/operations/group.py:170: error: Property "uid" defined in "Group" is read-only
volumes/fs/operations/group.py:171: error: Property "gid" defined in "Group" is read-only

volumes/fs/operations/versions/subvolume_base.py: note: In class "SubvolumeBase":
volumes/fs/operations/versions/subvolume_base.py:45: error: Name 'uid' already defined on line 33
volumes/fs/operations/versions/subvolume_base.py:45: error: "Callable[[SubvolumeBase], Any]" has no attribute "setter"
volumes/fs/operations/versions/subvolume_base.py:49: error: Name 'gid' already defined on line 37
volumes/fs/operations/versions/subvolume_base.py:49: error: "Callable[[SubvolumeBase], Any]" has no attribute "setter"
volumes/fs/operations/versions/subvolume_base.py:53: error: Name 'mode' already defined on line 41
volumes/fs/operations/versions/subvolume_base.py:53: error: "Callable[[SubvolumeBase], Any]" has no attribute "setter"

Fixes: https://tracker.ceph.com/issues/44393
Signed-off-by: Michael Fritch <mfritch@suse.com>