Fully clean up before each round of benchmarks in RangeFindBenchmark.cpp
Fully clean up before each round of benchmarks in RangeFindBenchmark.cpp

Summary: [Folly] Fully clean up before each round of benchmarks in `RangeFindBenchmark.cpp`.

The `vstr` and `vstrp` globals need to be cleaned up before each round of benchmarks.

Reviewed By: @​@​nbronson

Differential Revision: D2467254

floxard/folly,sonnyhu/folly,mqeizi/folly,SeanRBurton/folly,renyinew/folly,juniway/folly,stonegithubs/folly,arg0/folly,charsyam/folly,SeanRBurton/folly,lifei/folly,PPC64/folly,SeanRBurton/folly,sonnyhu/folly,facebook/folly,rklabs/folly,clearlylin/folly,leolujuyi/folly,renyinew/folly,fw1121/folly,clearlylin/folly,KSreeHarsha/folly,Hincoin/folly,KSreeHarsha/folly,Orvid/folly,charsyam/folly,alexst07/folly,arg0/folly,mqeizi/folly,leolujuyi/folly,SeanRBurton/folly,Orvid/folly,Orvid/folly,brunomorishita/folly,PPC64/folly,facebook/folly,alexst07/folly,fw1121/folly,clearlylin/folly,PoisonBOx/folly,lifei/folly,sonnyhu/folly,PPC64/folly,fw1121/folly,Hincoin/folly,stonegithubs/folly,gaoyingie/folly,stonegithubs/folly,arg0/folly,PoisonBOx/folly,mqeizi/folly,KSreeHarsha/folly,gaoyingie/folly,sonnyhu/folly,renyinew/folly,alexst07/folly,arg0/folly,charsyam/folly,PoisonBOx/folly,lifei/folly,gaoyingie/folly,fw1121/folly,rklabs/folly,stonegithubs/folly,Orvid/folly,Hincoin/folly,stonegithubs/folly,juniway/folly,charsyam/folly,PPC64/folly,floxard/folly,floxard/folly,arg0/folly,leolujuyi/folly,fw1121/folly,brunomorishita/folly,facebook/folly,mqeizi/folly,KSreeHarsha/folly,alexst07/folly,Hincoin/folly,brunomorishita/folly,rklabs/folly,leolujuyi/folly,loversInJapan/folly,clearlylin/folly,facebook/folly,Hincoin/folly,leolujuyi/folly,Orvid/folly,loversInJapan/folly,rklabs/folly,PPC64/folly,renyinew/folly,brunomorishita/folly,floxard/folly,mqeizi/folly,juniway/folly,rklabs/folly,loversInJapan/folly,gaoyingie/folly,loversInJapan/folly,alexst07/folly,lifei/folly,juniway/folly,brunomorishita/folly,floxard/folly,clearlylin/folly,gaoyingie/folly,KSreeHarsha/folly,SeanRBurton/folly,loversInJapan/folly,PoisonBOx/folly,PoisonBOx/folly,facebook/folly,juniway/folly,lifei/folly,renyinew/folly,sonnyhu/folly