When running multi-threaded tests with the JSTestCase class, resmoke.py eventually returns a single exit code for that test case. The exit code is currently set to the return code of the process that finishes last. Ideally, the exit code should be changed so that if one of the threads had failed (and not necessarily the last thread), then the final exit code from resmoke.py should be nonzero as well regardless of what the last thread returned.