Summary: Fixed a crash bug that incorrectly parse deprecated options in options_helper
Test Plan:
run db_bench with an old options file with memtable_prefix_bloom_probes
./db_bench --options_file=AN_OLD_OPTIONS_FILE --num=100 --benchmarks=fillseq
Reviewers: sdong, IslamAbdelRahman
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D59787