tools/sharelog_to_parquet: Fix repeatedly opening the parquet file when reading a growing sharelog
tools/sharelog_to_parquet: Fix repeatedly opening the parquet file when reading a growing sharelog

btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool