ldb files about goque

[nbmoa]

We encounter the same issue, but calling the CompactRange from the underlying levelDB doesn't fix the issue completely.
We use the DiskQueue as a persistent FIFO for our messages, so when we restart the service and don't loose data.

Before CompactRange call:
Queue is empty, it has the complete size of 830MB and consists of roughly 500 files. Most of the ldb files are between 1.6MB and 2MB.

After CompactRange call:
Queue is still empty :), it has a complete size of 700MB and consists of roughly 400 files. Now only ldb files with the size between 1.6MB and 2MB are left, all files that had a smaller size vanished.