Summary:
I just realized that when we run parallel valgrind we actually don't run the parallel tests under valgrind (we run the normally)
This patch make sure that we run both parallel and non-parallel tests with valgrind

Test Plan: DISABLE_JEMALLOC=1 make valgrind_check -j64

Reviewers: andrewkr, yiwu, lightmark, sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D62469