ceph: update wanted caps after resuming stale session

mds contains an optimization, it does not re-issue stale caps if
client does not want any cap.

A special case of the optimization is that client wants some caps,
but skipped updating 'wanted'. For this case, client needs to update
'wanted' when stale session get renewed.

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>