Fixed race condition in tests
Fixed race condition in tests

kaedroho/rust-rocksdb,spacejam/rust-rocksdb,kaedroho/rust-rocksdb,tempbottle/rust-rocksdb,spacejam/rust-rocksdb,spacejam/rust-rocksdb,kaedroho/rust-rocksdb,tempbottle/rust-rocksdb,tempbottle/rust-rocksdb