nfsd: nfserr_jukebox in nlm_fopen should lead to a retry

When v3 NLM request finds a conflicting delegation, it triggers
a delegation recall and nfsd_open fails with EAGAIN. nfsd_open
then translates EAGAIN into nfserr_jukebox. In nlm_fopen, instead
of returning nlm_failed for when there is a conflicting delegation,
drop this NLM request so that the client retries. Once delegation
is recalled and if a local lock is claimed, a retry would lead to
nfsd returning a nlm_lck_blocked error or a successful nlm lock.

Fixes: d343fce1 ("[PATCH] knfsd: Allow lockd to drop replies as appropriate")
Cc: stable@vger.kernel.org # v6.6
Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>