After SERVER-48773 was fixed, a few tests are still failing due to forking after creating new threads, which TSAN currently does not support and is resulting in the thread being killed. We can fix this by setting die_after_fork=0 in TSAN_OPTIONS, which disables the behavior.

Unfortunately, there is no way to limit the change to only the death tests. While disabling the behavior is unsupported, it appears we only ever do this as part of our death tests anyway (the test harness is multithreaded and forks a thread that then dies).