nfsd: fix endianness breakage in TEST_STATEID handling

->ts_id_status gets nfs errno, i.e. it's already big-endian; no need
to apply htonl() to it.  Broken by commit 174568 (NFSD: Added TEST_STATEID
operation) last year...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>