SeekRandomWhileWriting

Summary: as title

Test Plan: ran it

Reviewers: igor, haobo, yhchiang

Reviewed By: yhchiang

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17751
Don't dump rocksdb version on IOS
Dont build version if compiling for IOS
make corruption_test:CompactionInputErrorParanoid deterministic

Summary:
it writes ~10M data, default L0 compaction trigger is 4, plus 2 writer
buffer, so that can accommodate ~6M data before compaction happens for
sure. I guess encoding is doing a good job to shrink the data so that
sometime, compaction does not get triggered. I get test failure quite
often.

Test Plan: ran it multiple times and all got pass

Reviewers: igor, sdong

Reviewed By: sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17775