NFS: SEEK is an NFS v4.2 feature

Somehow the nfs_v4_1_minor_ops had the NFS_CAP_SEEK flag set, enabling
SEEK over v4.1.  This is wrong, and can make servers crash.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Tested-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>