Summary:
When a DB is opened, RocksDB creates an empty WAL file. When the DB is reopened and the WAL is empty, the min log number to keep is not advanced until a memtable flush happens. If a process crashes soon after reopening the DB, its likely that no memtable flush would have happened, which means the empty WAL file is not deleted. In a crash loop scenario, this leads to empty WAL files accumulating. Fix this by ensuring the min log number is advanced if the WAL is empty.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/11409

Test Plan: Add a unit test

Reviewed By: ajkr

Differential Revision: D45281685

Pulled By: anand1976

fbshipit-source-id: 0225877c613e65ffb30972a0051db2830105423e