nfsd4: use xdr_truncate_encode
nfsd4: use xdr_truncate_encode

Now that lengths are reliable, we can use xdr_truncate instead of
open-coding it everywhere.

Signed-off-by: J. Bruce Fields <51738506c1b2ccb0761f23bdc612c93babf738ea@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs