MFC: nfsserver/nfs_serv.c 1.108; explicitly set `error' to 0 in
nfsrv_noop() to deal with the NFSv3 case where nfsm_reply() does
not do it for us. This fixes an mbuf leak and a failure to correctly
return an error reply for bad authorisation or unknown procedure
numbers. Unlike the corresponding revision in -current, this affects
only NFSv3 requests.

Approved by: re