mgr/volumes: type convert uid and gid to int

mgr/volumes: type convert uid and gid to int

This fix is only needed in nautilus. The issue
was observed during upstream teuthology testing in CentOS 7.5
machines.

  File "/usr/share/ceph/mgr/volumes/fs/async_cloner.py", line 153, in do_clone
    bulk_copy(fs_handle, src_path, dst_path, should_cancel)
  File "/usr/share/ceph/mgr/volumes/fs/async_cloner.py", line 144, in bulk_copy
    cptree(source_path, dst_path)
  File "/usr/share/ceph/mgr/volumes/fs/async_cloner.py", line 134, in cptree
    sync_attrs(fs_handle, d_full_dst, stx)
  File "/usr/share/ceph/mgr/volumes/fs/async_cloner.py", line 77, in sync_attrs
    fs_handle.lchown(target_path, source_statx["uid"], source_statx["gid"])

The issue wasn't observed in master/octopus teuthology
testing.

Signed-off-by: Ramana Raja <rraja@redhat.com>