crash_test to trigger fail points other than file appending more frequently
crash_test to trigger fail points other than file appending more frequently

Summary:
For half of the crash_test run, disable fail point for file appending, in order to trigger other fail point more frequently.
Also, tune crash test parameter a little bit for it to initialize faster.

Test Plan: Run crash_test and make sure it issues db_stress commands as expected.

Reviewers: yhchiang, igor, rven, anthony, IslamAbdelRahman, kradhakrishnan

Reviewed By: kradhakrishnan

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D48843

wat-ze-hex/rocksdb,norton/rocksdb,wenduo/rocksdb,OverlordQ/rocksdb,jalexanderqed/rocksdb,Andymic/rocksdb,vmx/rocksdb,wat-ze-hex/rocksdb,wat-ze-hex/rocksdb,tsheasha/rocksdb,norton/rocksdb,OverlordQ/rocksdb,wenduo/rocksdb,SunguckLee/RocksDB,facebook/rocksdb,ryneli/rocksdb,vmx/rocksdb,norton/rocksdb,hobinyoon/rocksdb,jalexanderqed/rocksdb,flabby/rocksdb,SunguckLee/RocksDB,flabby/rocksdb,hobinyoon/rocksdb,Andymic/rocksdb,tsheasha/rocksdb,OverlordQ/rocksdb,facebook/rocksdb,tsheasha/rocksdb,ryneli/rocksdb,vmx/rocksdb,Andymic/rocksdb,ryneli/rocksdb,wenduo/rocksdb,wenduo/rocksdb,bbiao/rocksdb,bbiao/rocksdb,wat-ze-hex/rocksdb,norton/rocksdb,Vaisman/rocksdb,wat-ze-hex/rocksdb,wat-ze-hex/rocksdb,bbiao/rocksdb,flabby/rocksdb,norton/rocksdb,tsheasha/rocksdb,bbiao/rocksdb,bbiao/rocksdb,ryneli/rocksdb,Vaisman/rocksdb,jalexanderqed/rocksdb,flabby/rocksdb,facebook/rocksdb,hobinyoon/rocksdb,Andymic/rocksdb,SunguckLee/RocksDB,Andymic/rocksdb,wenduo/rocksdb,OverlordQ/rocksdb,hobinyoon/rocksdb,jalexanderqed/rocksdb,vmx/rocksdb,wat-ze-hex/rocksdb,wenduo/rocksdb,SunguckLee/RocksDB,facebook/rocksdb,facebook/rocksdb,OverlordQ/rocksdb,vmx/rocksdb,norton/rocksdb,jalexanderqed/rocksdb,Vaisman/rocksdb,Vaisman/rocksdb,jalexanderqed/rocksdb,tsheasha/rocksdb,Andymic/rocksdb,vmx/rocksdb,Andymic/rocksdb,facebook/rocksdb,flabby/rocksdb,bbiao/rocksdb,tsheasha/rocksdb,flabby/rocksdb,wat-ze-hex/rocksdb,bbiao/rocksdb,SunguckLee/RocksDB,flabby/rocksdb,jalexanderqed/rocksdb,ryneli/rocksdb,vmx/rocksdb,hobinyoon/rocksdb,norton/rocksdb,norton/rocksdb,wenduo/rocksdb,Vaisman/rocksdb,facebook/rocksdb,OverlordQ/rocksdb,SunguckLee/RocksDB,OverlordQ/rocksdb,tsheasha/rocksdb,Andymic/rocksdb,vmx/rocksdb,hobinyoon/rocksdb,bbiao/rocksdb,SunguckLee/RocksDB,Vaisman/rocksdb,Vaisman/rocksdb,hobinyoon/rocksdb,wenduo/rocksdb,facebook/rocksdb,tsheasha/rocksdb,ryneli/rocksdb,hobinyoon/rocksdb,SunguckLee/RocksDB,ryneli/rocksdb