Get rid of old nfsstat options no longer used.

The "-M" and "-N" options for nfsstat were used by the old NFS code and
have never done anything for the new NFS code.
This patch replaces code that assigns values to variables that are never
used with printf()s noting the options are ignored.
This has the side effect that it gets rid of warnings w.r.t. these
variables being assigned but never used, that occur for some builds.

Noticed during integration of the NFSv4.2 code.