nfs41: nfs41_sequence_free_slot

[from nfs41: separate free slot from sequence done]

Don't free the slot until after all rpc_restart_calls have completed.
Session reset will require more work.

As noted by Trond, since we're using rpc_wake_up_next rather than
rpc_wake_up() we must always wake up the next task in the queue
either by going through nfs4_free_slot, or just calling
rpc_wake_up_next if no slot is to be freed.

[nfs41: sequence res use slotid]
[nfs41: remove SEQ4_STATUS_USE_TK_STATUS]
[got rid of nfs4_sequence_res.sr_session, use nfs_client.cl_session instead]
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfs41: rpc_wake_up_next if sessions slot was not consumed.]
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfs41: nfs4_sequence_free_slot use nfs_client for data server]
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>