Unsupervise tasks before the scheduler kills them. Unblock before yield->fail

src/rt/rust_task.cpp

@@ -255,6 +255,9 @@ rust_task::yield(size_t time_in_us) {
         name, this, time_in_us);
 
     if (killed) {
+        if (blocked()) {
+            unblock();
+        }
         killed = false;
         fail();
     }