In cifs_call_async, server may respond as soon as I/O is submitted. Because
mid entry is freed on the return path, it should not be modified after I/O
is submitted.

cifs_save_when_sent modifies the sent timestamp in mid entry, and should not
be called after I/O. Call it before I/O.
Signed-off-by: NLong Li <longli@microsoft.com>
Reviewed-by: NPavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: NSteve French <smfrench@gmail.com>