Fix broken test double_bind
Fix broken test double_bind

Summary:
The sleep of 2 seconds was not enough time for mcrouter to startup and shutdown. This caused
the assertion on line 147 to consistently fail. I verified that the failure wasn't being caused by an
unexpected SO_REUSEPORT option.

Reviewed By: andreazevedo

Differential Revision: D13666658

fbshipit-source-id: 747cc65723d3649c1e83ebbb46c2afb3c126d9f5

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