Don't assert that all threads have stopped.

If assertions were enabled and we had a daemon thread running, the VM
would fail on exit.
diff --git a/vm/Thread.c b/vm/Thread.c
index 3102a47..2e982d8 100644
--- a/vm/Thread.c
+++ b/vm/Thread.c
@@ -410,8 +410,12 @@
 void dvmThreadShutdown(void)
 {
     if (gDvm.threadList != NULL) {
-        assert(gDvm.threadList->next == NULL);
-        assert(gDvm.threadList->prev == NULL);
+        /*
+         * If we walk through the thread list and try to free the
+         * lingering thread structures (which should only be for daemon
+         * threads), the daemon threads may crash if they execute before
+         * the process dies.  Let them leak.
+         */
         freeThread(gDvm.threadList);
         gDvm.threadList = NULL;
     }