Update db_bench description for unordered_write

[rbrasga]

Note: Please use Issues only for bug reports. For questions, discussions, feature requests, etc. post to dev group: https://groups.google.com/forum/#!forum/rocksdb or https://www.facebook.com/groups/rocksdb.dev

Expected behavior

DEFINE_bool(enable_pipelined_write, true,
            "Allow WAL and memtable writes to be pipelined");

DEFINE_bool(unordered_write, false,
            "**The writes to the main write queue in rocskdb goes through a different path**");

^ I'm not really sure what belongs there, even after reading: https://github.com/facebook/rocksdb/wiki/unordered_write

Actual behavior

DEFINE_bool(enable_pipelined_write, true,
            "Allow WAL and memtable writes to be pipelined");

DEFINE_bool(unordered_write, false,
            "Allow WAL and memtable writes to be pipelined");

^ Is the description really identical for both enable_pipelined_write and unordered_write?

Steps to reproduce the behavior

https://github.com/facebook/rocksdb/blob/master/tools/db_bench_tool.cc#L988

[ltamasi]

Thanks for reporting @rbrasga ! I've submitted a PR to fix this.

[rbrasga]

Great wording on the help! Thanks for the quick fix.