fix flaky test due to not enough rss memory
fix flaky test due to not enough rss memory

Summary: https://www.internalfb.com/intern/test/281474999287141/

Reviewed By: Happytreat

Differential Revision: D38504398

fbshipit-source-id: 4dfcdf7e6639d4b3c2b0473830fe0f9b6a38360b

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