valgrind_check to exit on test failures

valgrind_check to exit on test failures

Summary: Currently, valgrind_check doesn't fail on test failures, which creates confusion. valgrind_check should fail if test fails.

Test Plan: Manually change tests to return test failure or cause memory leak and see valgrind_check has the correct behavior.

Reviewers: anthony, yhchiang, IslamAbdelRahman, igor, kradhakrishnan, rven

Reviewed By: rven

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D43629