fix callPreviousSignalHandler()
fix callPreviousSignalHandler()

Summary:
If a previous handler was found, the code was missing the step of
actually re-raising the handler after restoring the old handler.

Test Plan: Verified that our service actually exits after receiving SIGTERM.

Reviewed By: tudorb@fb.com

FB internal diff: D1096360

mqeizi/folly,clearlylin/folly,sakishum/folly,SammyK/folly,leolujuyi/folly,stonegithubs/folly,ykarlsbrun/folly,colemancda/folly,chjp2046/folly,doctaweeks/folly,upsoft/folly,SeanRBurton/folly,KSreeHarsha/folly,brunomorishita/folly,project-zerus/folly,lifei/folly,gavioto/folly,cole14/folly,brunomorishita/folly,wildinto/folly,rklabs/folly,Orvid/folly,stonegithubs/folly,bsampath/folly,mqeizi/folly,bowlofstew/folly,renyinew/folly,Orvid/folly,tempbottle/folly,nickhen/folly,loversInJapan/folly,Orvid/folly,Eagle-X/folly,floxard/folly,mqeizi/folly,Hincoin/folly,constantine001/folly,chjp2046/folly,gavioto/folly,guker/folly,wildinto/folly,charsyam/folly,leolujuyi/folly,yangjin-unique/folly,renyinew/folly,constantine001/folly,tomhughes/folly,romange/folly,clearlylin/folly,loverszhaokai/folly,CJstar/folly,gavioto/folly,clearlinux/folly,PoisonBOx/folly,SeanRBurton/folly,romange/folly,bsampath/folly,raphaelamorim/folly,facebook/folly,bobegir/folly,clearlinux/folly,facebook/folly,chjp2046/folly,loverszhaokai/folly,chjp2046/folly,bobegir/folly,cppfool/folly,wildinto/folly,bowlofstew/folly,romange/folly,shaobz/folly,alexst07/folly,shaobz/folly,lifei/folly,bowlofstew/folly,PoisonBOx/folly,Orvid/folly,unmeshvrije/C--,KSreeHarsha/folly,theiver9827/folly,doctaweeks/folly,leolujuyi/folly,bikong2/folly,SammyK/folly,guker/folly,ykarlsbrun/folly,tomhughes/folly,SeanRBurton/folly,doctaweeks/folly,upsoft/folly,colemancda/folly,cole14/folly,alexst07/folly,shaobz/folly,bsampath/folly,brunomorishita/folly,kernelim/folly,ykarlsbrun/folly,doctaweeks/folly,yangjin-unique/folly,CJstar/folly,sonnyhu/folly,gaoyingie/folly,renyinew/folly,bowlofstew/folly,tomhughes/folly,floxard/folly,rklabs/folly,Hincoin/folly,juniway/folly,unmeshvrije/C--,fw1121/folly,gavioto/folly,fw1121/folly,bikong2/folly,ykarlsbrun/folly,bobegir/folly,clearlinux/folly,loversInJapan/folly,charsyam/folly,cole14/folly,bikong2/folly,loverszhaokai/folly,loverszhaokai/folly,nickhen/folly,renyinew/folly,PoisonBOx/folly,PoisonBOx/folly,ykarlsbrun/folly,bobegir/folly,lifei/folly,unmeshvrije/C--,wildinto/folly,bsampath/folly,project-zerus/folly,reddit/folly,PPC64/folly,raphaelamorim/folly,upsoft/folly,alexst07/folly,xzmagic/folly,facebook/folly,SammyK/folly,KSreeHarsha/folly,facebook/folly,nickhen/folly,zhiweicai/folly,juniway/folly,bikong2/folly,rklabs/folly,stonegithubs/folly,Eagle-X/folly,clearlylin/folly,floxard/folly,romange/folly,juniway/folly,unmeshvrije/C--,loversInJapan/folly,bsampath/folly,fw1121/folly,theiver9827/folly,sonnyhu/folly,facebook/folly,constantine001/folly,SammyK/folly,gaoyingie/folly,hongliangzhao/folly,PPC64/folly,constantine001/folly,sakishum/folly,kernelim/folly,arg0/folly,cppfool/folly,loverszhaokai/folly,wildinto/folly,lifei/folly,arg0/folly,leolujuyi/folly,Hincoin/folly,project-zerus/folly,arg0/folly,gaoyingie/folly,sonnyhu/folly,xzmagic/folly,project-zerus/folly,tempbottle/folly,cole14/folly,stonegithubs/folly,colemancda/folly,KSreeHarsha/folly,reddit/folly,alexst07/folly,clearlylin/folly,yangjin-unique/folly,loversInJapan/folly,sakishum/folly,guker/folly,charsyam/folly,cppfool/folly,arg0/folly,guker/folly,PPC64/folly,Hincoin/folly,raphaelamorim/folly,fw1121/folly,kernelim/folly,CJstar/folly,CJstar/folly,mqeizi/folly,charsyam/folly,CJstar/folly,yangjin-unique/folly,project-zerus/folly,tempbottle/folly,tomhughes/folly,sonnyhu/folly,Hincoin/folly,shaobz/folly,hongliangzhao/folly,nickhen/folly,bowlofstew/folly,upsoft/folly,shaobz/folly,bobegir/folly,theiver9827/folly,zhiweicai/folly,tempbottle/folly,SeanRBurton/folly,gaoyingie/folly,sonnyhu/folly,romange/folly,theiver9827/folly,PoisonBOx/folly,kernelim/folly,renyinew/folly,brunomorishita/folly,tempbottle/folly,yangjin-unique/folly,colemancda/folly,kernelim/folly,bikong2/folly,mqeizi/folly,colemancda/folly,doctaweeks/folly,juniway/folly,SeanRBurton/folly,tomhughes/folly,chjp2046/folly,cppfool/folly,alexst07/folly,loversInJapan/folly,reddit/folly,PPC64/folly,rklabs/folly,juniway/folly,raphaelamorim/folly,gaoyingie/folly,stonegithubs/folly,lifei/folly,zhiweicai/folly,hongliangzhao/folly,reddit/folly,cole14/folly,Eagle-X/folly,clearlylin/folly,clearlinux/folly,nickhen/folly,floxard/folly,clearlinux/folly,gavioto/folly,unmeshvrije/C--,sakishum/folly,brunomorishita/folly,fw1121/folly,reddit/folly,xzmagic/folly,xzmagic/folly,leolujuyi/folly,constantine001/folly,hongliangzhao/folly,zhiweicai/folly,guker/folly,SammyK/folly,upsoft/folly,xzmagic/folly,raphaelamorim/folly,KSreeHarsha/folly,Eagle-X/folly,theiver9827/folly,sakishum/folly,unmeshvrije/C--,hongliangzhao/folly,floxard/folly,Orvid/folly,cppfool/folly,zhiweicai/folly,arg0/folly,rklabs/folly,PPC64/folly,Eagle-X/folly