NFSv4.1 Increase NFS4_DEF_SLOT_TABLE_SIZE

Increase NFS4_DEF_SLOT_TABLE_SIZE which is used as the client ca_maxreequests
value in CREATE_SESSION.  Current non-dynamic session slot server
implementations use the client ca_maxrequests as a maximum slot number: 64
session slots can handle most workloads.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>