[t:4288], fix performance issue in unlock_worker_op in stress tests

git-svn-id: file:///svn/toku/tokudb@39608 c7de825b-a66e-492c-adef-691d508d4ae1

src/tests/threaded_stress_test_helpers.h

@@ -121,15 +121,17 @@ static void lock_worker_op(struct worker_extra* we) {
 
 static void unlock_worker_op(struct worker_extra* we) {
     ARG arg = we->thread_arg;
+    if (arg->lock_type != STRESS_LOCK_NONE) {
         toku_pthread_mutex_lock(we->operation_lock_mutex);
         if (arg->lock_type == STRESS_LOCK_SHARED) {
             rwlock_read_unlock(we->operation_lock);
         } else if (arg->lock_type == STRESS_LOCK_EXCL) {
             rwlock_write_unlock(we->operation_lock);
         } else {
-        assert(arg->lock_type == STRESS_LOCK_NONE);
+            assert(false);
         }
         toku_pthread_mutex_unlock(we->operation_lock_mutex);
+    }
 }
 
 static void *worker(void *arg_v) {