Summary:
We don't propagate TableProperty::oldest_key_time on compaction and just write the default value to SST files. It is more natural to default the value to 0.

Also revert db_sst_test back to before #2842.
Closes https://github.com/facebook/rocksdb/pull/3079

Differential Revision: D6165702

Pulled By: yiwu-arbug

fbshipit-source-id: ca3ce5928d96ae79a5beb12bb7d8c640a71478a0