Relax an assertion in Compaction::ShouldStopBefore
Relax an assertion in Compaction::ShouldStopBefore

Summary:
In some case, it is possible to have two concesutive SST files might sharing
same boundary keys.  However, in the assertion in Compaction::ShouldStopBefore,
it exclude such possibility.

This patch fix this issue by relaxing the assertion to allow the equal case.

Test Plan: rocksdb tests

Reviewers: IslamAbdelRahman, kradhakrishnan, sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D55875

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