Fix ASAN issues
Fix ASAN issues

Summary: use-after-free.

Reviewed By: jmswen

Differential Revision: D3309817

fbshipit-source-id: 566ba46629f90a645f24fe18e5a40d360437727f

yqzhang/mcrouter,yqzhang/mcrouter,facebook/mcrouter,facebook/mcrouter,yqzhang/mcrouter,facebook/mcrouter,yqzhang/mcrouter,facebook/mcrouter