Fix format bug
Fix format bug

Summary: Fix addition bug instead of string concat

Test Plan: ?? It compiles?  The only call paths are when syscalls fail, it would be a lot of work to stub them out

Reviewed By: mshneer@fb.com

Subscribers: trunkagent, doug, njormrod, folly-diffs@

FB internal diff: D1679713

Tasks: 5604354

Signature: t1:1679713:1415925209:ed05d3d1ce3e7e8db32c4afc86c5f24748d9c65b

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