NFS: Don't swap bytes in nfs4_construct_boot_verifier()

The SETCLIENTID boot verifier is opaque to NFSv4 servers, thus there
is no requirement for byte swapping before the client puts the
verifier on the wire.

This treatment is similar to other timestamp-based verifiers.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>