Fixes#7230
When a cluster goes down during file replication, the chunk upload process
would fail after a limited number of retries. Once the remote cluster came
back online, those failed uploads were never retried, leaving the clusters
out-of-sync.
This change enables the RetryForever flag in the UploadOption when
replicating chunks between filers. This ensures that upload operations
will keep retrying indefinitely, and once the remote cluster comes back
online, the pending uploads will automatically succeed.
Users no longer need to manually run fs.meta.save and fs.meta.load as
a workaround for out-of-sync clusters.
cc2edfaf68