Fix clang build
Fix clang build

Test Plan:
build it

Reviewed By: alikhtarov@fb.com

Subscribers: mathieubaudet, alikhtarov

FB internal diff: D1606293

evertrue/mcrouter,apinski-cavium/mcrouter,leitao/mcrouter,yqzhang/mcrouter,is00hcw/mcrouter,is00hcw/mcrouter,apinski-cavium/mcrouter,nvaller/mcrouter,evertrue/mcrouter,apinski-cavium/mcrouter,evertrue/mcrouter,seem-sky/mcrouter,nvaller/mcrouter,zhlong73/mcrouter,seem-sky/mcrouter,glensc/mcrouter,easyfmxu/mcrouter,tempbottle/mcrouter,easyfmxu/mcrouter,nvaller/mcrouter,facebook/mcrouter,zhlong73/mcrouter,tempbottle/mcrouter,facebook/mcrouter,leitao/mcrouter,evertrue/mcrouter,is00hcw/mcrouter,reddit/mcrouter,glensc/mcrouter,facebook/mcrouter,synecdoche/mcrouter,synecdoche/mcrouter,seem-sky/mcrouter,leitao/mcrouter,zhlong73/mcrouter,zhlong73/mcrouter,is00hcw/mcrouter,yqzhang/mcrouter,glensc/mcrouter,easyfmxu/mcrouter,synecdoche/mcrouter,synecdoche/mcrouter,reddit/mcrouter,seem-sky/mcrouter,tempbottle/mcrouter,apinski-cavium/mcrouter,easyfmxu/mcrouter,yqzhang/mcrouter,leitao/mcrouter,glensc/mcrouter,nvaller/mcrouter,yqzhang/mcrouter,reddit/mcrouter,tempbottle/mcrouter,reddit/mcrouter,facebook/mcrouter