NFS: Make trace_nfs4_setup_sequence() available to NFS v4.0

This tracepoint displays information about the slot that was chosen for
the RPC, in addition to session information.  This could be useful
information for debugging, and we can set the session id hash to 0 to
indicate that there is no session.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>