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, and the issue
was observed during upstream teuthology testing.

   File "/usr/share/ceph/mgr/volumes/fs/async_cloner.py", line 114, in cptree
     copy_file(fs_handle, d_full_src, d_full_dst, mo, st.st_uid, st.st_gid)
   File "/usr/share/ceph/mgr/volumes/fs/fs_util.py", line 97, in copy_file
     fs.chown(dst, uid, gid)
   File "cephfs.pyx", line 855, in cephfs.LibCephFS.chown
      TypeError: uid must be an int

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

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