Fixed some potential RCU problems.

- Added missing unlock.
- Removed synchonization from dynamic array operation (not needed
  and the dynamic array will be removed anyway).

src/common/dynamic-array.c

@@ -81,7 +81,7 @@ static int da_resize(da_array_t *array, da_resize_type_t type)
 	dbg_da("Old items pointer: %p\n", old_items);
 
 	// wait for readers to finish
-	synchronize_rcu();
+	//synchronize_rcu();
 	// deallocate the old array
 	dbg_da("RCU synchronized, deallocating old items array at address %p."
 	         "\n", old_items);
@@ -205,7 +205,7 @@ void da_destroy(da_array_t *array)
 	rcu_set_pointer(&array->items, NULL);
 	pthread_mutex_unlock(&array->mtx);
 
-	synchronize_rcu();
+	//synchronize_rcu();
 	free(old_items);
 	pthread_mutex_destroy(&array->mtx);
 }

src/knot/server/xfr-handler.c

@@ -866,6 +866,7 @@ static int xfr_client_start(xfrworker_t *w, knot_ns_xfr_t *data)
 	/* Handle errors. */
 	if (ret != KNOT_EOK) {
 		pthread_mutex_unlock(&zd->xfr_in.lock);
+		rcu_read_unlock();
 		dbg_xfr("xfr: failed to create XFR query type %d: %s\n",
 		        data->type, knot_strerror(ret));
 		close(data->session);