The global snaprealm would be created and then destroyed immediately
every time when updating it.

URL: https://tracker.ceph.com/issues/54362Signed-off-by: NXiubo Li <xiubli@redhat.com>
Reviewed-by: NJeff Layton <jlayton@kernel.org>
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>