NFSv4: Fix retry issues with nfs41_test/free_stateid

_nfs41_free_stateid() needs to be cached by the session, but
nfs41_test_stateid() may return NFS4ERR_RETRY_UNCACHED_REP (in which
case we should just retry).

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Tested-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>