rocksdb_replicator: fix a log on missing update (#603)
rocksdb_replicator: fix a log on missing update (#603)

A straightforward change: the log happens under if check result.sequence != expected_seq_no, so the log should just reflect that. The current approach will result in a segfault when it happens (because of accessing response.updates which is still empty)

Also only log&metrics when result.sequence > expected_seq_no 
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