NFSv4.1: Handle errors correctly in nfs41_walk_client_list

Both nfs41_walk_client_list and nfs40_walk_client_list expect the
'status' variable to be set to the value -NFS4ERR_STALE_CLIENTID
if the loop fails to find a match.
The problem is that the 'pos->cl_cons_state > NFS_CS_READY' changes
the value of 'status', and sets it either to the value '0' (which
indicates success), or to the value EINTR.

Cc: stable@vger.kernel.org # 3.7.x: 7b1f1fd1: NFSv4/4.1: Fix bugs in
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>