NFSD: TEST_STATEID should not return NFS4ERR_STALE_STATEID

According to RFC 5661, the TEST_STATEID operation is not allowed to
return NFS4ERR_STALE_STATEID.  In addition, RFC 5661 says:

15.1.16.5.  NFS4ERR_STALE_STATEID (Error Code 10023)

   A stateid generated by an earlier server instance was used.  This
   error is moot in NFSv4.1 because all operations that take a stateid
   MUST be preceded by the SEQUENCE operation, and the earlier server
   instance is detected by the session infrastructure that supports
   SEQUENCE.

I triggered NFS4ERR_STALE_STATEID while testing the Linux client's
NOGRACE recovery.  Bruce suggested an additional test that could be
useful to client developers.

Lastly, RFC 5661, section 18.48.3 has this:

 o  Special stateids are always considered invalid (they result in the
    error code NFS4ERR_BAD_STATEID).

An explicit check is made for those state IDs to avoid printk noise.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>